Last week I started having problems with cd-r's. I've used the same brand for a year with no problems, now they won't work.
I had to take my powerbook in for a hinge replacement, and when I got it back they'd replaced the superdrive chassis mount. No explanation as to why, but I'm guessing some sort of damage or misalignment.
Hey presto, my disks work again, so if you have this problem and are still under warranty, I'd definitely suggest taking the book in for a checkup.
Cheers,
J.