I had the same trouble in my 2.2 but with DVD-Rs. When my graphics chip failed, they replaced the motherboard, and the DVD-ROM started working again. However, lately it's stopped working. I'm going to take it to an apple store and see if they can replace the drive. I've got three year applecare, I hope you do too, but I don't think it's a very expensive part.
Try blowing in there or something, it could be dust.