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Will this .ini hack fix the XUL Runner startup problem in Firefox 5.0 without causing other problems.

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I have been running Firefox without difficulty for many months.

I just accepted the update to 5.0.

I get the XULRunner version number error on startup in one of two accounts on a WinXP SP3 (fully patched) machine. I have tried the suggestions -- clean install of Firefox -- no effect.

The one thing that did work is to change the firefox .ini file to accept Gecko version 2.0 to 5.0 rather than 5.0 to 5.0. This enables me to run Firefox and do this report.


Is the .ini hack likely to screw up anything else?

Also -- the problem exists with ZoneAlarm on or off.

I also noted that, though I used the 5.0 installer, the Help/About box says 4.0 -- but the Help/trouble shooting says 5.0.


Best regards,

Jim Matey

I have been running Firefox without difficulty for many months. I just accepted the update to 5.0. I get the XULRunner version number error on startup in one of two accounts on a WinXP SP3 (fully patched) machine. I have tried the suggestions -- clean install of Firefox -- no effect. The one thing that did work is to change the firefox .ini file to accept Gecko version 2.0 to 5.0 rather than 5.0 to 5.0. This enables me to run Firefox and do this report. Is the .ini hack likely to screw up anything else? Also -- the problem exists with ZoneAlarm on or off. I also noted that, though I used the 5.0 installer, the Help/About box says 4.0 -- but the Help/trouble shooting says 5.0. Best regards, Jim Matey

James R. Matey trɔe

All Replies (1)

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You will have to try again to download and install Firefox.
It shouldn't be necessary to edit files that way to make Firefox work.
It is always possible that more files got corrupted.

You can try to do a custom installation in a different program folder (e.g. Mozilla Firefox 5) to see if that works.
Also try to disable your security (anti-virus) software and other software that could corrupt downloaded files.

If the updater wasn't able to update all the files and older versions are still present then you need to do a clean reinstall.

Download a fresh Firefox copy and save the file to the desktop.

  • Uninstall your current Firefox version.
  • Do not remove personal data when you uninstall the current version.

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

  • It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.

Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.