OK - just happened on 481... same thing - I had added a fuser ield to my library, click OK... then a crash, now MC won't load. Great!
Must be something else? (Other than a 482/ratings issue) Want some info or a crash report or anything?
I'm running Vista, no A/V, nothing else at all, I think. Let me know what info you need to diagnose the problem.
Thanks!