Osx Rejecting Blank Discs


I have recently updated to iTunes 5, on OSX 10.4.2

I have been using a batch of blank discs successfully for the past 3 months. Now, if I insert one, the drive spins up for a few seconds, spins back down, and ejects the disc. I've tried about 6 different pieces of media with no success. Is there an issue with the iTunes update that would have affected this? I successfully burned a disc with Toast Titanium approx 5 days ago, but now, I can't even get my Mac to not regurgitate a disc from the same batch.

Thanks in advance for your help