''Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.''
I am using Windows10, Version 20H2 (OS Build 19042.928) with all available patches installed as of 04/14/2021, and am using Firefox 87.0 (64-bit) as the default browser. I have suddenly begun to get the subject error message (Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.) in Firefox, whenever I try to open an email web link from within Thunderbird. Until a few days ago, the email web link always opened up in a new Firefox browser tab.
If I change the default browser to something else, the email web link opens in a new tab in that browser.
I have tried every solution that has been recommended in this support forum to no avail. The error pops up even when Firefox has been started in safe mode. I have created new profiles to no avail. I have even gone so far as to totally uninstall Firefox, then manually rename all of the Firefox directories in my user profile and then install a clean version of Firefox. So far, I have not been able to get rid of the problem.
Any suggestions would be appreciated.
All Replies (8)
Thanks for the reply but I've gone through those and they do not resolve the problem. If deleted, Firefox creates the parent.lock file every time that it loads. On my two other Windows10 PCs, I do not have this problem with Thunderbird email web links, even though the parent.lock file is also present.
if you open the Task Manager and kill the FireFox process(s), will a single new instance of FF open?
i mean, after you kill the process(s), then right click on the FF icon and open in admin mode and also monitor the Task Manager at same time.
Yes. Firefox opens, loads, works and closes normally. It just refuses to open a new tab (and generates the error message) whenver I click on a web link from inside a Thunderbird email.
i see. thanks for the clarification.
what happens when you right click on the link in Tbird, and have it opened up in new window?
It just generates the same error message, whether I directly click on the link or right click on it and tell Tbird to open the link in a new window.
You did cite testing the issue in FF while in safemode.
But did you mean FF safe mode or Windows Safe mode?
If not the Win Safemode, then give this a try for testing the issue at hand, ie windows safemode w/networking options.
I have tried loading Firefox in safe mode while running Windows10 in safe mode with networking. When I try to open a web link from inside Tbird the error message is still generated.