FWIW, I am experiencing the same “tearing” display issue in After Effects CS6. I’m running a 6 core Mac Pro, with an ATI 5870 HD card. The same files display fine in CS5.5, but the tearing in CS6 is really annoying. I’m partially resigned to replacing this card so I can implement the Mercury Playback engine features in Premiere Pro, as well as the new 3D rendering in After Effects. Thus, I suppose a Nvidia card is in my future, but I’d like to know for sure that this will fix the tearing issue.
Looking for advice on solutions!