It's a known issue in CCC and ATI sucks @ drivers.
Before I bought my very expensive 4870 X2, I was using an 8800 GTX that had served me well for over a year. Occasionally nvidia had a bad driver release, but they were very active with their community and they had a tendancy to fix their mistakes in an expedient manner.
When I went with the ATI card, I was encouraged by some forum posts saying that ATI had stepped up their driver quality and that the ATI driver problems were a thing of the past. We are now into the 4th driver release since the 48xx series came out and I can say, without any hesitation, that in terms of performance AND stability, the CCC 8.11 and accompanying driver are worse than the 8.10 CCC release, and possibly the 8.9 also. ATI does not acknowledge any problem and really doesn't say much of anything. And we have yet another month to hope that the next driver release will fix the issues that we're currently having with previous drivers. It's absolutely intollerable. This will be the last time ATI or AMD gets a dime from me and it brings me no joy to say that because I'm the kind of person who thinks competition is a good thing. Unfortunately AMD does not seem to understand that it's in competition with anybody.