This has been happening periodically since the beginning of the week. Its symptoms include blocks of white 'flashes' while scrolling or watching video, along with graphical artifacts being left behind. To me, it sounds very much like the graphics glitches that plague the new Penryn MBPs; a glitch which 10.5.3 was supposed to fix. Here's a link to an article about 10.5.3 and the graphics glitch: http://www.macsimumnews.com/index.p...hics_problem_still_exists_in_os_x_1053_video/. 10.5.3, it points out, hasn't fixed a thing. In fact, judging from the comments and my own experience it's only gotten worse; what before was only a problem on Penryn-based MBPs is now a problem for me on my Summer 2007 Santa Rosa. I have never had a problem with graphics before installing 10.5.3 (besides the well-known 'Leopard Lag' in things like the 3D Dock and Exposé) and it only seems to happen while on battery power after returning from sleep. Is anyone else with a Santa Rosa (or even older) MBP noticing this now that you've installed 10.5.3?