For over a week I've not been able to open FF--I get a message that says "FF is already running but is not responding. To open a new window, you must first close the existing FF process, or restart your system." I've tried the following: scanning my computer completely for malware and viruses (got rid of all threats); going into Task Manager and looking for multiple versions of the mozilla.exe or firefox.exe (in fact there were none at all listed); downloading various versions of FF (3, 4, and 5). None of this has made a difference. I've been using Google Chrome for some time, as a result. But all my bookmarks are in FF, and they're very necessary for my work. I also like FF.
Maybe a stupid question, but since you did not mention it, did you try rebooting the computer? Whenever I get that issue with firefox, a reboot fixes it.
Hi, I realized after posting the thread that I didn't include that as one of my troubleshooting procedures--yes, I rebooted it numerous times each day (for the past 11 days or so). In fact, the problem got worse: FF at first would at least open up for about 15 minutes or so and then start having problems. But as of a week ago it wouldn't even open up anymore!
Restart your computer.
After it restarts, don't try to start Firefox.
Go to your Firefox profile folder in the appdata (or type this in your search box - %APPDATA%\Mozilla\Firefox\Profiles\). Get the xxxx.default profile open.
Delete the lock file parent.lock
If this cannot be deleted, either the profile is unavailable for FF or a problem with the partition. Make sure the profile is not read only.
If these methods do not support to solve the issue, you have to create a new profile and migrate to the new one. Use this link to learn how to. Hope this helps :)
Maybe you just need a complete firefox reinstallation (uninstall and reinstall)
Just in case, copy all files under C:/Program Files/Mozilla Firefox/ and paste it somewhere else. Then uninstall Firefox using normal uninstall or Revo. Make sure firefox program is completely uninstall... Then reboot...
Then download firefox 5 (latest one) and install it. After install, don't try to open firefox just yet, reboot once and then try to open firefox...
The solution mentioned above will solve the issue. If you have a doubt like it is using by other application, you have to disable recently added plugins. To check whether it is locked by a process you can use a process viewer or something run something like LockHunter against the executable (firefox.exe) file