Hi Techiegal.
I may be a bit late for you but I have just encountered the same problem after updating to Firefox 3.6. CC kept saying close Firefox when it definitely WAS closed. Never had this problem with CC before. I deleted then reinstalled CC but still no go. Downloaded Eusing Free registry cleaner and that worked very well and has backup also but I prefer CC as I have been using it for years with no problems. Anyway, I then tried shutting down and restarting Vista, ran CC and Bingo, worked like a charm but I guess you have figured it out by now. Thought I would reply just in case.
Cheers. Barry.