My 667 DVI powerbook combo drive has stopped recognizing DVDs; it spins them for a few seconds then ejects the DVD without saying anything 90% of the time, occasionally it tells me they're blank. I'm running 10.3.2, which I recently installed, about two weeks ago...I've checked for any firmware updates and I have the most current firmware already. If anyone has any advice on how to fix this, I'd really appreciate it.