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Firefox won't start - getting "could not find Mozilla runtime" message when clicking on Firefox icon - safe mode does't work either - get the same message

  • 4 replies
  • 5 have this problem
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  • Last reply by Gnospen

bayuser
bayuser
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Discovered at approximately 10PM Eastern time on 3/23/15 that Firefox will not initialize. Get the message "Could not find Mozilla runtime" when clicking on the Firefox icon. Can't start in safe mode because 1) can't bring Firefox up to use the menu and 2) holding the shift key and clicking on the icon gives me the same "Could not find Mozilla runtime" message. I have never updated Firefox manually. I am running Windows/XP. Firefox has been working A-OK for months and months and I use it daily. Don't know which release of Firefox that I'm using and can't bring it up to check. If you tell me how to find out, I'll check. I have found that a firefox.exe does exist in the mozilla firefox folder.

Also Running Norton 360 and looked in the Norton 360 log and could find nothing relating to Firefox, Mozilla, or runtime error. However, when selecting both the support and help options in Norton 360, I get the same "could not find Mozilla runtime" message. I didn't think that Norton used Firefox.

Please note: I tried to automatically add the troubleshooting information and it did not work. I then tried to do the manual option but can't find the "Help-Troubleshooting information" at the top of the screen. Maybe this is because I am using AOL to type this message instead of Firefox.

Thanks for helping me solve this problem so I can use Firefox.

Discovered at approximately 10PM Eastern time on 3/23/15 that Firefox will not initialize. Get the message "Could not find Mozilla runtime" when clicking on the Firefox icon. Can't start in safe mode because 1) can't bring Firefox up to use the menu and 2) holding the shift key and clicking on the icon gives me the same "Could not find Mozilla runtime" message. I have never updated Firefox manually. I am running Windows/XP. Firefox has been working A-OK for months and months and I use it daily. Don't know which release of Firefox that I'm using and can't bring it up to check. If you tell me how to find out, I'll check. I have found that a firefox.exe does exist in the mozilla firefox folder. Also Running Norton 360 and looked in the Norton 360 log and could find nothing relating to Firefox, Mozilla, or runtime error. However, when selecting both the support and help options in Norton 360, I get the same "could not find Mozilla runtime" message. I didn't think that Norton used Firefox. Please note: I tried to automatically add the troubleshooting information and it did not work. I then tried to do the manual option but can't find the "Help-Troubleshooting information" at the top of the screen. Maybe this is because I am using AOL to type this message instead of Firefox. Thanks for helping me solve this problem so I can use Firefox.

All Replies (4)

cor-el
cor-el
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  • Top 10 Contributor
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Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

  • Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

  • (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
  • (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then also create a new profile.

Gnospen
Gnospen
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Use explorer to navigate to C:\Program Files\Mozilla Firefox\ and try to start firefox.exe from there

Your profile holds your settings, shortcuts, saved password ...... You can find your profile by: 

  Start → Run
  type in %APPDATA%
   Click OK. A Windows Explorer window will appear.
   In this window, choose Mozilla → Firefox → Profiles.

For safety you can copy this some where.

bayuser
bayuser Question owner
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Thank you for the quick response but this did not work. Let me be certain that I did the correct thing. I tried to start Firefox as you suggested from C:\program files/mozilla firefox/firefox.exe and got the same "could not find Mozilla runtime" message. 

I did not do the start - run steps because I thought that starting firefox from the exe should work first.  Is this correct?

If I should do the start run steps with the exe being successful, let me know. Also please let me know some details about this copy step. What am I copying and where should I put the copy? Thank you.

Gnospen
Gnospen
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Your right starting Firefox was the first step. My suggestion about run...... %appdata% is for you to find your personal profile for FF. Copying this to another location for safe-keeping.

Follow Cor-El 's advice and make an uninstall and a new install.