No problems here, at least nothing that has anything to do with Firefox, that is.

Renderosity, however is a different story, what with the disabled spell checker and that you can't use your mouse to copy/paste in a message box and all kind of other annoying cra... I mean... features like that.

But that has nothing to do with Firefox, far as I know.
I'm not real big on the latest version though. Used to be you could close down your only tab and have just an "Untitled" tab up there, now you have to close the browser if you want to close out your only tab, or start a new tab, then close the open one. No idea who came up with that idea, but he needs to turn in his browser coding license, IMO. ;-)

I've always had trouble with Firefox and certain websites with a lot of Java. Parts of McAfee's site as well as much of Comcast's customer area being notable examples. I have to use IE for those.
I suppose it's because some web developers just figure everyone is using IE, since it comes with Windows. They need to be fired, too. Tortured first though, and I don't mean the comfy chair either. ;-)