This has recently become more of an issue on my early 2008 mbp w/ 512 video memory. When I am scrolling on web sites or in iChat or really any program for that matter, my screen sometimes becomes distorted. Included are 3 shots from 3 very different programs. iChat, FireFox & InDesign where this happened. I also notice when videos are playing in a website and i scroll the screen most of the time I get these fast flickering rectangular boxes in the video or flash area. It seems to tear in places. I have taken it to apple 3 times for this issue and they have tested and tested the video. At one point, they claim, running a video loop test for 36hours straight w/ no faults found. Please see attached. Please advise.