I hate to dredge up the past here, but last October I had an issue with a new installment of CS4. This Is The Thread
The problem that I had was that CS4 was not rendering the shadow gradients correctly. It was showing color banding instead of shadows. I was told this was because I have a cheap LCD, this was not the case. I figured up a setting that fixed the issue. But I can't remember what it was. Can any of you guys think of what it might have been. This problem exists in PS, Bridge, and ACR. I just had to reinstall windows and I find myself in the same position.
Thanks guys.