The display on my non-unibody MacBook Pro sometimes gets pinstripes. Every other pixel is a pixel-wide, gray vertical stripe down the height of the screen, all the way across. Sometimes the display is fine, then it goes pinstripey. I cannot detect a pattern as to anything triggering the stripes.

I actually took this in to the Genius Bar already, and the diagnosis was that it's probably NOT an issue with my GPU (lines don't appear on the external display I use frequently), but I'm wondering if I can a) get confirmation on this, b) get some advice as to what parts I may be able to get to fix this myself.