Firefox gives a "Firefox already running" error despite reinstalling repeatedly
The version I've installed recently is v68.0.1 (x64), my OS is WIndows 7.
This error began after my PC suffered a significant error that crashed out most active programs, including Firefox; attempting to start Firefox again caused the relatively common "Firefox is already running but is not responding. The old process must be closed to open a new window" error to pop p, with the options "Close Process" and "Cancel". Clicking either button caused the error message to become unresponsive, and after a few minutes a second identical error would pop up (without the original one ever closing); sometimes when there were several unresponsive errors it would sometimes crash Windows Explorer if I tried to interact with new popups. In Task manager there were multiple Firefox processes running, but attempting to "End Process" would not end two of them, they simply stayed there active. By this point I'd resolved all other issues from the PC crash, as far as I could see, and no other programs were showing any issues at all.
I restarted the PC several times but the error persisted; I was able to create a new profile in Profile Manager but this did not stop the error. I uninstalled Firefox and manually deleted the parent.lock files in the Appdata/Roaming/Mozilla/Firefox/Profiles folder (they were 'in use by Firefox' if I didn't uninstall and restart the PC first, even though no Firefox processes were listed as running in Task Manager). I then reinstalled Firefox, but I still got the same error popup (though it at least didn't become unresponsive and crash Windows Explorer any more - but I still have the un-ending processes in Task Manager).
By this point I've (after backing them up!) uninstalled Firefox and manually deleted everything Firefox-related in the Appdata/Roaming folder, everything Firefox-related in the Appdata/Local folder, and under Program Files (X86), then reinstalled Firefox again. The error persists, unchanged.
Any further suggestions on what I could try would be welcome, I'm stumped by this. Chrome and Avast Browser work fine; Internet Explorer works about as well as it ever does. No new programs had been installed around the time of the problem (to my knowledge) and I've been using Firefox for years on this PC.
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- I-ejenti Engumsebenzisi: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36
Do a clean reinstall of the current Firefox release and delete the Firefox program folder before installing a fresh copy of the current Firefox release.
- download the Firefox installer and save the file to the desktop
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 the current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including personal data in profiles created by other Firefox versions
Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.
- (64-bit Firefox) "C:\Program Files\Mozilla Firefox\"
- (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"
- it is important to delete the Firefox program folder to remove all the files and make sure there are no problems with files that were leftover after uninstalling
Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, 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 you can create a new profile to test if your current profile is causing the problem.
It is possible that your firewall or other security software blocks or restricts Firefox without informing you, possibly after detecting changes (update) to the Firefox application. Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access for Firefox and the plugin-container process and the updater process.
Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.
Many thanks; I tried most of the above in my original attempts to fix it but I've tried again, deleting all remaining files after uninstalling (and backing up profile data, of course) so nothing remains from the previous Firefox install, restarting, and reinstalling. I've gone through Firewall and Avast Antivirus and removed any special rules relating to Firefox.
I still get a "Firefox is already running" error after reinstalling from a freshly downloaded installer, when starting up for the first time. A Firefox process starts running after this error appears and is still impossible to terminate from Task Manager.
I've run from Safe Mode with networking - the error appears with the same features as above. Likewise, any other user accounts on the PC suffer the same issue.