Well, 10.6.3 has a lot of graphics issues and bugs.
for me, whenever i am playing a game, and i just go to windowed mode to check e-mail or something, and then i go back again to full screen mode, the screen goes pink, and i don't know why. even I degraded to 10.6.2, the issuse went away.
Just wait for 10.6.4, or downgrade to 10.6.2
I have a MBP 13 and had got it in Dec 09 and had updated my Mac os 10.6 to 10.6.3 around a week back. Everything went fine but I noticed after rebooting my laptop after the install, the screen brightness reduced. Initially I though that the brighntess must have been set low but even after increasing the settings to max, the screen brightness was very low as compared to before the install. I even tried resetting the PROM and adjusting my colour profile but nothing changed. I then popped in the DVD which came along and downngraded the OS back to 10.6 and the screen brighness returned to it's previous level. Can anyone suggest me with a solution as I am have tried installing the update twice but faced with same problem.