Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.
Cannot understand why I keep getting this message as I don't have any old Firefox process open to my knowledge. The strange thing is that if I use Safe Mode with networking, Firefox works ok. Can someone help me with this issue as I can't figure out what the problem is.
This message would be normal if you close Firefox, and then reopen before waiting for it to finish. On a fast computer you have to wait a few seconds to not get the error, on a very slow one maybe one minute.
I believe this is not the question you are asking, but just to cover that situation.
When does this message appear? Have had any problems you know of with multiple versions or profiles?
kerft: It appears whenever I try to open Firefox 68.3.0esr (x64-en-US). Don't know why as it only occurs in regular mode but not if I if I use Safe Mode with networking.
Does it appear if you launch the browser in Firefox SAFE MODE? (Not to be confused with Windows Safe Mode with Networking.) http://kb.mozillazine.org/Safe_mode
If the problem returns, you might try disabling all of your extensions, if you have any, and restart FF in the normal mode to see if the problem goes away.
If you still have the problem, then try making a new profile (type about:profiles in the URL field). Name the new profile "test" or some such, and do not load any extensions. See if you still have the problem.
If you can run FF in the normal mode without extensions, then disable all of the extensions. Next, enable one of them, restart FF in the normal mode, and see what happens. If FF works, then enable a second extension and see what happens. And so on... hope this helps!
* HP Pavilion Desktop 510-p114
* Windows 10 Home 22H2 19045.4291
* Firefox 124; Thunderbird 115.8
Know this is an old thread but decided I had to post the solution to my stange FF issue in case someone else runs into the same problem. Went into the Windows 10 Pro Task Manager and found 6 instances of Firefox running under the DETAILS section after Firefox had been closed down. As soon as I right-clicked on each instance of the Firefox process and told it to End Task, the error message
Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.
went away for me.
So if anyone else running Windows 10 is running into this problem after closing Firefox down, it may be due to the same problem.
So if anyone else running Windows 10 is running into this problem after closing Firefox down, it may be due to the same problem.
Well, you didn't identify the of the problem, only a symptom. The advice above regarding Mozilla Safe Mode and/or disabling installed extensions would apply as a way to identify the cause of multiple processes that had not closed down when you closed Firefox.
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