Yesterday I asked the question here: https://support.mozilla.org/en-US/questions/1085073 ...about how I opened FF and it behaved like a completely new installation (no bookmarks, no passwords), then I closed it and it returned to normal on reboot. Well, almost normal - bookmarks, plugins etc are all back where they were, but all my passwords have disappeared including the one for my Mozilla support account. So I had to create a new account (the password reset did not deliver the promised email).