Wow, nobody has a clue? Am I the only one running this combination and seeing this problem?
I don't have a clue, but here is what I can tell you: I have a year and a half old MBP with the 8600 chipset, (2.6 with 6G RAM) and CS4 is running excellent on mine. However, I find that Open GL sucks so bad even on my Mac Pro with high-end video card -- especially messes up screen rendering and re-draws, but also color and banding -- that I disabled it COMPLETELY on both systems. Once disabled, I have had zero issues with system performance, zero issues with CS4 screen redraws and zero issues with color or banding.
Note that to disable Open GL completely, I suggest you uncheck all the tabs, even the ones under "Advanced," because IIRC some of them remained enabled on my box even if the first main "enable" button was un-checked. It's been so long I cannot remember the exact issue, but I know I had to go back in and manually turn every option off to get it running right on mine.
Cheers,