Abort mission Abort mission.... hahaha
Hmm, you rebooted i assume. Sometimes I've noticed firefox not starting and there were a whole bunch of dead processes running in task manager, rare, but it has happened.
Did you delete profiles? Backup your c:/documents and settings/user name/Application Data/Mozilla folder than delete it, see if that works.
You may also have an event notification in event viewer telling you why it hangs.