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. … (read more)
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.