Firefox comes in two or more folders on all computers. They are;

Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And two folders in the profile of each user on the computer for each Firefox profile for that user.

If you remove the Firefox folder, the user folders would not be affected.

+Win Firefox uses two locations for the Firefox profile folder. Location used for the main profile in "AppData\Roaming" that keeps your personal data.

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

Location used for the disk cache and other temporary files in "AppData\Local".

• C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profile

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

If you think you might need to rebuild your Firefox setup, you can make a backup of your profile folder. The first article has suggestions for that, but making a copy of your entire Profiles folder in a safe place also would work.

• Back up and restore information in Firefox profiles
• Profiles - Where Firefox stores your bookmarks, passwords and other user data
• Recover important data from an old profile
• https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files (the AppData folder is a hidden folder)

FredMcD said

Firefox comes in two or more folders on all computers. They are; Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And two folders in the profile of each user on the computer for each Firefox profile for that user. If you remove the Firefox folder, the user folders would not be affected. +Win Firefox uses two locations for the Firefox profile folder. Location used for the main profile in "AppData\Roaming" that keeps your personal data.

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

Location used for the disk cache and other temporary files in "AppData\Local".

• C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profile

I have uninstalled and reinstalled Firefox v.56 three times ( a procedure which usually corrected this problem in the past). No way is it going to start for me! Not from the Start Menu, Desktop Icon, or, Pinned Taskbar Icon!

Thank you for reminding me where the all-important profile folders and files are to be found but I am not a computer nerd (just 33 years of DOS and Windows experience!) and I have no idea what I should be looking for, let alone how I should go about changing what's there!

I noticed that the Mozilla Maintenance Service folder is nested under Program Files (x86) while the program files proper are nested under Program Files (64 bit apps). Is this OK? I've been using the 64-bit version of Firefox since March/17 when all updates (for 64-bit platforms) subsequently defaulted to this version.

For many years my Firefox has existed happily under the auspices of AVG Internet Security (full paid up versions) so why would AVG now find fault with Firefox? If it is now being blocked, why? I can find no "block list" in my AVG software. No other applications on this desk computer are being "blocked".

Can anybody here give me a clue as to what is preventing my Firefox from starting and what can I do to fix this?

Since you have been uninstalling and installing might as well do one more. Not seen where you get your installer from so use this Full Version Installer from here : https://www.mozilla.org/en-US/firefox/all/

Some people have had to move to the Extended Release Version due to age of cpu and lack of support for drivers and for MS Win 7. Might want to check out the ESR here : https://www.mozilla.org/en-US/firefox/organizations/

Please let us know if this solved your issue or if need further assistance.

Do you get any error messages when you try to start Firefox?

If you check the Windows 7 Task Manager, does Firefox appear to be "stalled"? I generally call that up using Ctrl+Shift+Esc, and then click the Processes tab. Firefox is listed under firefox.exe, potentially with multiple processes depending on the number of tabs opening at startup.

You can choose to display multiple activity columns (e.g., Read Bytes, Write Bytes) so you can get a sense of whether Firefox is doing anything or is just dead.

Pkshadow said

Since you have been uninstalling and installing might as well do one more. Not seen where you get your installer from so use this Full Version Installer from here : https://www.mozilla.org/en-US/firefox/all/

I have used both methods: Firefox Installer.exe and Firefox Setup 56.0.1.exe. I'm up to 5 re-installs now - no cigar!

Interestingly, in each case, Administrative Events reported that the installation WAS successful.

My system is only four years old - an Asus Z77 platform I put together with the very finest components - and has worked flawlessly all this time. Never had a problem like this before.

jscher2000 said

Do you get any error messages when you try to start Firefox? If you check the Windows 7 Task Manager, does Firefox appear to be "stalled"? I generally call that up using Ctrl+Shift+Esc, and then click the Processes tab. Firefox is listed under firefox.exe, potentially with multiple processes depending on the number of tabs opening at startup. You can choose to display multiple activity columns (e.g., Read Bytes, Write Bytes) so you can get a sense of whether Firefox is doing anything or is just dead.

I don't get ANY message(s) when trying to start Firefox. It just ignores me and does nothing.

When I looked at the Event Viewer on the day this occurred I see this Application Error:

"Level Date and Time Source Event ID Task Category Error 14/10/2017 8:47:24 AM Application Error 1000 (100) "Faulting application name: firefox.exe, version: 56.0.1.6484, time stamp: 0x59d2c74f Faulting module name: LVPrcInj01.dll_unloaded, version: 0.0.0.0, time stamp: 0x4be4c077 Exception code: 0xc0000005 Fault offset: 0x00000000003bbeb8 Faulting process id: 0x13e4 Faulting application start time: 0x01d344ea938e2bd4 Faulting application path: C:\Program Files (x86)\Mozilla Firefox\firefox.exe Faulting module path: LVPrcInj01.dll Report Id: d313fa77-b0dd-11e7-a720-60a44c37ac61"

The information report I get is:

"14/10/2017 8:47:25 AM Windows Error Reporting 1001 None "Fault bucket 493748977, type 27 Event Name: BEX64 Response: Not available Cab Id: 0

Problem signature: P1: firefox.exe P2: 56.0.1.6484 P3: 59d2c74f P4: LVPrcInj01.dll_unloaded P5: 0.0.0.0 P6: 4be4c077 P7: 00000000003bbeb8 P8: c0000005 P9: 0000000000000008 P10:

Attached files: C:\Users\Gumpy\AppData\Local\Temp\WER8EB6.tmp.WERInternalMetadata.xml

There were warnings that preceded the failure event, such as:

"Warning 13/10/2017 1:45:05 AM Microsoft-Windows-User Profiles Service 1530 None "Windows detected your registry file is still in use by other applications or services. The file will be unloaded now. The applications or services that hold your registry file may not function properly afterwards."

"Error 13/10/2017 10:58:08 AM NvStreamSvc 1 None "The description for Event ID 1 from source NvStreamSvc cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer," and "NvStreamSvc NvVAD endpoint registration failed [0]"

"Error 14/10/2017 8:26:51 AM Microsoft-Windows-WMI 10 None "Event filter with query ""SELECT * FROM __InstanceModificationEvent WITHIN 60 WHERE TargetInstance ISA ""Win32_Processor"" AND TargetInstance.LoadPercentage > 99"" could not be reactivated in namespace ""//./root/CIMV2"" because of error 0x80041003. Events cannot be delivered through this filter until the problem is corrected."

Unfortunately, my level of expertise is not sufficient to understand this cryptic language.

Is this useful information?

Thanks, most of that doesn't mean anything to me, either. These are the parts that get my attention:

Oldstrommer said

...
Faulting module path: LVPrcInj01.dll
...
Event Name: BEX64

I searched LVPrcInj01.dll and found pages referencing Logitech QuickCam. Is that a product you use? Firefox wouldn't normally need to fire up a webcam at startup unless perhaps there was an add-on that uses it or you were restoring a page from a previous session that used the camera.

Does that same DLL seem to be implicated in later problems, or is that the only thing you found in the logs?

I think a BEX or BEX64 event is a memory violation that Windows views as suspicious and therefore kills the program. It can indicate a malware problem. Our support article lists free cleaning tools you can use as a supplement to your regular security software: Troubleshoot Firefox issues caused by malware.

jscher2000 said

If you check the Windows 7 Task Manager, does Firefox appear to be "stalled"? I generally call that up using Ctrl+Shift+Esc, and then click the Processes tab. Firefox is listed under firefox.exe, potentially with multiple processes depending on the number of tabs opening at startup.

I've had to access Task manager a lot over the years when (you guessed it) Firerfox would freeze up (as in "not responding"). But, since this failure occurred, when I call Task Manager up it shows Firefox is NOT active - which is reasonable since Firefox WON'T START!

Do you by any chance have Malwarebytes installed  ? If so : would you disable (or remove) it and see if that will make a
difference  ?

jscher2000 said

I searched LVPrcInj01.dll and found pages referencing Logitech QuickCam. Is that a product you use? Firefox wouldn't normally need to fire up a webcam at startup unless perhaps there was an add-on that uses it or you were restoring a page from a previous session that used the camera. Does that same DLL seem to be implicated in later problems, or is that the only thing you found in the logs? I think a BEX or BEX64 event is a memory violation that Windows views as suspicious and therefore kills the program. It can indicate a malware problem. Our support article lists free cleaning tools you can use as a supplement to your regular security software: Troubleshoot Firefox issues caused by malware.

Thanks for your input jscher2000. I really appreciate your help.

Yes I have a Logitech camera but it is only used for Skyping (is that a word now?). I have been depending on my AVG and PC-Tuneup to keep a watchful eye on it. The thought of malware being implicated had not yet crossed my mind.

The file LVPrcInj01.dll doesn't show up until that fateful morning (Saturday, Oct.14), the day after the Firefox Update. It occurs repeatedly after every reinstall and attempted start of Firefox. I think you're definitely onto something here.

If it has something to do with malware and the corrupting of some of my files, it certainly hasn't been detected by my AVG Security Suite. I've run numerous scans every day hoping it will find the problem and fix it. No such luck. Bummer.

Thanks very much for the heads up on the free cleaning tools. That's where I'm heading next.

I'm not gonna give up because I REALLY like Firefox!

After using the mal-scanners, if there is still a problem; Start the Windows Task Manager First. Then start Firefox. Does FF show up and disappear?

Happy112 said

Do you by any chance have Malwarebytes installed  ? If so : would you disable (or remove) it and see if that will make a
difference  ?

And the answer is .......... (drum roll)

Happy112 said

Do you by any chance have Malwarebytes installed  ? If so : would you disable (or remove) it and see if that will make a
difference  ?

Malwarebytes was installed after the firefox non-start event only as a supplemental tool to find any malware that my regular security software (AVG Internet Security) missed. Nothing found! Uninstalled today.

FredMcD said

After using the mal-scanners, if there is still a problem; Start the Windows Task Manager First. Then start Firefox. Does FF show up and disappear?

Did as you suggested. Windows Task Manager shows no start of Firefox. Nothing at all.

Let’s do a full clean re-install;

Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them. Do not rename the Mozilla Thunderbird folder if there is one.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. If all goes well, remove the OLD folders when you are done. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

OK Folks - I have GOOD News!

After futzing about for days trying to detect malware on my desktop drives I finally got around to following up a suggestion from jscher2000 and took down my Logitech Webcam Pro 9000 - physically and all the installed software.

After the usual re-boot of Win7 AND re-installing Firefox - BINGO!

I was jumping for joy. Such happiness to have my Firefox back!

Now I am going to re-install the Logitech webcam and hope to hell it won't interfere with FF again.

Thanks to all of you who took the time to post here with helpful suggestions. 'jscher2000 you are an Angel!!!

That was very good work. Well done. Please flag your last post as Solved Problem so others will know.

You should contact Logitech Webcam support and ask questions.

FredMcD said

That was very good work. Well done. Please flag your last post as Solved Problem so others will know. You should contact Logitech Webcam support and ask questions.

My Logitech Webcam Pro 9000 is an old (legacy) model and support is limited. But I was able to download a newer version of their software and that was what I used to reinstall.

I should tell you that when I initially tried to reinstall from the original software CD it would not work. On the first install page, where it asked what language to use (and where English would usually be the default) there was only a string of consecutive numbers (12345...90, repeating non-stop). The original drivers and utility software had functioned properly for about seven years until last week.

So it is likely that something new in my system (newest FF Update perhaps?) didn't like the old Logitech software. I admit I never had occasion to update it and it didn't have an auto check built in. It was tempting to be suspicious of malware but repeated scans with my AVG Internet Security, Malwarebytes, SUPERAntiSpyware, adwcleaner, and tdsskiller came up clean. The leading candidate is a problem driver.

In any case, I am very happy to have this issue resolved after many fretful days during which I had to take some time away from it to avoid losing my mind and punching a hole in the wall.

Much love to you all.