What do you mean by "FORCE a close"? Do you mean "Crash"? If so, is there an error message?

Firefox did not "crash". A window popped up that said Firefox was going to close. It would not allow any action other than to click "OK". It was not only VERY annoying, it was rude! I do not believe that software should ever act like that. There was no error message, and when I re-opened Firefox, the only pop-up message was one which offered an add-on, called "remember me" or some such #*^##@* thing. -Dave