Something like that happened to me last week when iDVD crashed. I had a ton of yellow pixels on the desktop. It's almost as if a color in my wallpaper had been swapped with yellow. Strange though, if I brought up an image and moved it around. Those yellow dots moved with it. So that confirmed that it was not pixels on the desktop, it was a color problem. Just as an experiment, I tried to toggle my screen resolution up and down as a way to refresh the display. That interim blue screen that is displayed showed perfectly until my desktop picture was again displayed. The yellow dots still appeared. I figured iDVD left something in a bad state when it crashed. (It was my fault, I accidentally deleted some project assets while I was still encoding.) I took a screen shot, viewed it, and confirmed that the yellow pixels displayed on the screenshot. I then rebooted. The problem had gone away, and the yellow dots did not appear on the screenshot. May have been VRAM corruption or something. I hope it's not a sign of things to come, or that my video card has gone south. Nevertheless, a reboot fixed it. I hope I never see that again.