I belatedly updated to Firefox 184.108.40.206 and lost all my saved passwords without a pause. The password file (signon2.txt (curious; it should be signon.txt)), the key3.db file and the cert8.db file were all there but the password were not being filled in and the show password dialog was completely blank. In spite of this the bookmarks were showing up correctly.
The first thing to do in a situation like this is to take a bakup. Then I typed in 'about:config' into the browser and changed the signon.SignOnFileName to signon2.txt still no dice.
The next thing to do is to create new profile and copy the files from your old profile into the new folder. In case you have never had to create a new profile before; you need to start firefox from the command line using the -ProfileManager parameter. So did it work? not exactly but we are on the right track.
Immidiately after starting with the new profile, this error was generated: