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XULRunner Error msg when try to start Firefox: Platform version '43.0.1' is not compatible with minVersion>=49.0.2 maxVersion<=49.0.2; tried reinstall, no help

d_e_j
d_e_j
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Firefox worked previously, but now when attempting to start the application I get this "XULRunner" error message: "Error: Platform version '43.0.1' is not compatible with 

    minVersion >= 49.0.2
    maxVersion <= 49.0.2"

Several times I have tried uninstalling Firefox, making sure I deleted all related files and directories, and reinstalling Firefox, but the uninstall/reinstall does not fix the problem.

The computer is a Dell running Windows XP SP3. Firefox was working fine until a month or so ago. I welcome any help or guidance you can provide. Thank you for the assistance.

Firefox worked previously, but now when attempting to start the application I get this "XULRunner" error message: "Error: Platform version '43.0.1' is not compatible with minVersion >= 49.0.2 maxVersion <= 49.0.2" Several times I have tried uninstalling Firefox, making sure I deleted all related files and directories, and reinstalling Firefox, but the uninstall/reinstall does not fix the problem. The computer is a Dell running Windows XP SP3. Firefox was working fine until a month or so ago. I welcome any help or guidance you can provide. Thank you for the assistance.

All Replies (5)

Oxylatium
Oxylatium
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That sounds like an addon not compatible with FF50. Do you have the same error message when starting FF in safe mode? https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

If not, disable add-on one by one to find the faulty add-on.

d_e_j
d_e_j Question owner
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I could not find a way to start Firefox in Safe Mode, so I uninstalled and reinstalled it. Immediately after the reinstall, Firefox started without issue. However, the next time I turned on the computer and attempted to launch it, I got a "Couldn't load XRE functions" message and the application would not launch. Is this still possibly an add-on problem? The menu from right-clicking my Firefox icon does not have Safe Mode as a choice. If there is a parameter that goes with firefox.exe to start it in Safe Mode, I could do that from the "Run" command line.

the-edmeister
the-edmeister
  • Moderator
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Before you reinstalled Firefox did you delete the Mozilla Firefox folder in program files to gat a clean installation?

As I recall with XP, the uninstaller routine doesn't always remove the base Mozilla Firefox folder that Firefox program files are installed in, and on occasion some old files may get stuck there and aren't removed.

d_e_j
d_e_j Question owner
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Yes, after running Uninstall from the Control Panel, I did a search for any file or folder names containing "Firefox" or "Mozilla" and deleted all that turned up, so I think I got rid of all the old files.

Any idea what would cause the "Couldn't load XRE functions" message?

the-edmeister
the-edmeister
  • Moderator
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Beyond deleting the Firefox program files folder and reinstalling Firefox using the full offline installer, the only other thing that I have heard of causing that "Couldn't load XRE functions" message was an anti-virus application (Zone Alarm specifically). As mentioned in this support article - two different sections: https://support.mozilla.org/en-US/kb/firefox-wont-start-find-solutions#w_xulrunner-error https://support.mozilla.org/en-US/kb/firefox-wont-start-find-solutions#w_firefox-will-not-start-after-updating

Please try installing Firefox again. Don't even bother using the Windows Control Panel > Program / Application Remove process (sorry, don't know what that is called in Win10) - just delete the Firefox program files folder.

Then download the "offline" installer from here: https://www.mozilla.org/en-US/firefox/all/ And install Firefox after closing all web browsers that may be open.

Modified by the-edmeister