This just happened today, but about once every 5 minutes, my MacBook 2007 is seemingly cutting up the image on the screen and making abstract designs that are glitching in and out along with other colors. It's very strange, and I just press the F3 key a couple times to choose the window I want, and it'll go back to normal for about 5 minutes again. Any ideas about what this is?
Reset the PRAM by holding down cmd-opt-P-R for two chimes while the machine is booting up. If it keeps happening after that, don't hesitate to take it into the Apple store if you are still under warranty.