Start the bad Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. Is the problem still there?

While still in Safe Mode,

Type about:support in the address bar and press Enter. Under the main banner, press the button; Copy Text To Clipboard.. Then in the reply box at the bottom of this page, do a right click in the box and select Paste. This will show us your system details. No Personal Information Is Collected.

zwarmapapa I've only just started trying Firefox 64bit on Windows but have had no problems with it so far. I've used Firefox 64 bit on Linux for years.

I would make a guess that Firefoxon the problem mchine may be failing to install rather than crashing.

I am not familiar with WerFault.exe but it seems it is the error reporting service of Windows accessible from Control panel -> Administrative Tools -> Component Services -> Services Local -> Window error reporting ... OR ( services.msc) Maybe your event logs will give some indication of what is happening.

If Firefox 64bit is installed try to start it in safe mode by holdig down the shift key as it you click its icon. IF that does not work try using run (Winkey R) and appending -safe-mode to the command as explained in this article http://kb.mozillazine.org/Safe_mode#Windows

If Firefox 64 is installed and not starting up this is the best trouble shooting article http://kb.mozillazine.org/Browser_will_not_start_up Please read through that and try the suggestions.

Fred I have not been around for a few months now. Not sure if this is a Windows bug or an issue with my machine but my Firefox versions on Windows are not starting in safemode from the hold shift key methods (That method is not applicable to Linux). Does that work ok for you - I am guessing you use Windows.

Win 7. I have no problem starting to safe mode via shift. Are you holding down the shift during the startup?

Also, many users are having problems after installing FF v44.

Thanks for trying to help me!

- Starting with shift hold down shows no difference. 
- Appending -safe-mode to the shortcut and then running it shows no difference. 
- Using firefox 43 x64 shows no difference. 
- Using firefox 47 (nightly) x64 shows no difference. 
- Trying to start firefox x64 won't add anything to the windows event logs. 

I have no idea what it could be, the lack of errors messages, dumps and logs cause me to be unable to understand what it might be.

Start your Computer in safe mode with networking. Then start Firefox. Try Safe web sites. Is the problem still there?

Starting The Computer In Safe Mode;
Free Online Encyclopedia

Fred Thanks for the reply. Guess it is a glitch on this machine then. It is Win7 and I tried shift on starting Fx43 to 47including some 64bit versions. Not something I am going to troubleshoot, as long as I can use the commandline method.

zwarmapapa said

Thanks for trying to help me! - Starting with shift hold down shows no difference. - Appending -safe-mode to the shortcut and then running it shows no difference. .... I have no idea what it could be, the lack of errors messages, dumps and logs cause me to be unable to understand what it might be.

Are you able to access the Window event viewer directly,it should record details of a failed startup.

• Use:

 Start button  -> Control Panel -> System and Security
->  Administrative Tools ->  Event Viewer

• See http://windows.microsoft.com/en-gb/windows/what-information-event-logs-event-viewer

I tried booting in safe-mode, and guess what, in safe-mode firefox x64 works!

Now I just have to figure out why firefox x32 (x86) will start after a normal boot and why firefox x64 won't.

The event logs don't show any difference between before and after trying to start firefox x64 (after a normal boot).

There is an error with WMI that is constantly showing up after booting, but I don't think this is relevant to the firefox x64 problem.

The WMI error says: "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."

I'll try fixing it, rebooting and trying firefox x64 again, maybe something will be different then.

----------- 

Fixed the WMI error, but firefox x64 still won't start, and the event logs still don't show a difference between before and after starting/crashing firefox x64.

Good. I suppose that is at least some improvement.
You say it starts ok in safemode. So to be clear please confirm that you are talking here about Windows safemode making a difference.

Personally since Windows XP I have tried to avoid using Windows as much as possible. I probably do not have the necessary knowledge to help you on a specific Windows issue . As you now have WMI fixed presumably I was hoping the event logs are working properly again so you would now be seeing information about Fx64bit failing to start.

Some Windows forum may be able to assist with how to get event information e.g.

• http://www.sevenforums.com/index.php
  http://www.sevenforums.com/gtsearch.php?cx=partner-pub-7156303416008077%3Ahfslqp-2rmq&cof=FORID%3A9&ie=UTF-8&q=event+logs
  • http://www.sevenforums.com/tutorials/226084-event-viewer-open-use-windows-7-a.html

Because if Fx64bit is encountering a problem and failing to start Windows 7 should; I would think, have generated and logged events.

Alternatively, as Fx64bit is installed, and apparently not generating error events is FX itself generating crash information.

• See Troubleshoot Firefox crashes (closing or quitting unexpectedly)
  Mozilla Crash Reporter_viewing-reports-outside-of-firefox

If so are you able to get some of the Crash IDs

• See also Firefox hangs or is not responding - How to fix

You do not yet appear to have tried a clean reinstall. Please try that and say if it helps.

In this context this is where with Fx64bit you delete the program files before reinstalling again. {Take care to leave the x86 32 bit program files alone]
Whilst doing that also delete any fx64bit profile, but again take care to leave the Fx32bit profile alone. {Open fx32bit identify its profile using Menu -> Troubleshooting Info -> Show Folder ]

• See also Profiles - Where Firefox stores your bookmarks, passwords and other user data_how-do-i-find-my-profile

CLEAN INSTALL (Standard response): Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location. {So in this instance please do that as a separate step]

To do a clean reinstall of Firefox, please follow these steps: Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

I meant windows safe-mode indeed, firefox safe-mode didn't make a difference.

What does windows safe-mode do exactly that makes firefox x64 start then, but not after a normal boot?

Anyway, about the rest:

- I've looked for crash reports (in "%appdata%/Mozilla/Firefox/Crash Reports"), but nothing is there, firefox x64 doesn't even recreate the %appdata%/Mozilla folder. 

Checked for crash reports, there are none.

- I've tried removing the %appdata%/Mozilla folder, uninstalled every firefox installation, removed all their folders ("C:/Program Files (x86)/Mozilla Firefox" and "C:/Program Files/Mozilla Firefox"), restarted the system, and installed firefox x64 again. 

Is this not a clean install?

After fixing WMI, windows event logs still show no difference between before and after starting/crashing firefox x64.

Maybe this is the thing I need to fix first in order to get the firefox error message.

WerFault.exe will also never close when firefox x64 crashes.

Besides that, in services Windows Error Reporting Service is disabled, when trying to enable it (setting it to manually or automatic, doesn't matter), it gives an error "system can't find given path".

The path it shows is "C:\Windows\System32\svchost.exe -k WerSvcGroup", which exists, and the command also runs in cmd without throwing errors.

However, after running it in cmd, it doesn't seem to make a difference, services still say it is not running, and firefox x64 still won't add anything to the event logs.

I'll try to fix this and see if it makes a difference.

Removing apdata removes the profile not the program there are two separate locations. I think the Fx64 program files by default should be at.

   C:\Program Files\Mozilla Firefox  

As for why windows safe mode works when normal mode does not that is not something I can answer but a Windows forum could help or someone else here such as Fred may answer.

Later today I will try on a Windows7 machine and then post again to confirm the location of the program files and that the error event logging works for me. {Again someone else may answer first)

There was more behind the appdata thing, I'll post it without the - thing:

I've tried removing the %appdata%/Mozilla folder, uninstalled every firefox installation, removed all their folders ("C:/Program Files (x86)/Mozilla Firefox" and "C:/Program Files/Mozilla Firefox"), restarted the system, and installed firefox x64 again.

Anyway, I caused it to work again!

What I did was rightclick firefox.exe (of the x64 firefox), go to properties, compatibility, and then enable compatibility mode with "Windows 7".

Don't know why it works, probably because of the same reason windows safe-mode works as well.

Something in my Windows is probably fcked, installed and uninstalled a lot of sht on this PC years ago, things like Soluto and Advanced System Care and whatever else.

Besides that, I also toyed around a lot with that PC a long time ago, mostly enabling/disabling any windows feature I could find, just to see what it would do, lol.

I still don't know exactly what the problem is, but what does it matter, it works now.

Glad its working thanks for posting back with the solution

It is not normal to need to use compatibility Mode.
I can run FX32bit in XP, Win7, & Win10; and 64bit in Win7&10 without needing to use compatibility mode.

Startup Crashes often require a clean install of Firefox. In fact there are often no other options if safemodes fail to remedy the situation.