For the record, I'm pretty sure that you could have just closed the browser, deleted the .mozilla folder, and restarted Firefox. I tested it a dozen or so times on different VMs and it worked out well at resetting everything.I decided I didn't want to fight with this anymore and followed KGIII's instructions in post #7.
I mention it again because it's a pretty neat trick. I am not terribly surprised that it works. You can do that with all sorts of stuff. I wasn't sure if it'd work with Firefox, but it did. It's a trick worth remembering.