There is a fix to this problem already. You can find it here if you like:

http://www.opera.com/

(Jokes aside, I've heard of quite a few problems people have been having not just with Firefox updates, but with Firefox and it's ability to do Gmail properly, and sending them a message saying you have an issue, or asking them for help, doesn't seem to be getting results. Either they're totally ignoring people asking for help, and ignoring the bug reports, or, they're working very hard on trying to figure out what happened).