I just had this happen with my G5 iMac 2GHz - I've been burning data CD's and DVD's, burning home iMovie projects with iDVD, and ripping audio CD's with no problems. Suddenly last week, my superdrive won't read ANYTHING, blank DVD/CD's, commercial DVD/CD's, even discs I've recently burned on it.
I recently upgraded iTune and to 10.4.7, but this problem started a few days afterward. I've used Disk Utility, repaired permissions, and updated again to 10.4.7 using the Combo Update, with no help.
Any ideas would be appreciated. My iMac is 14 months old, and is covered by AppleCare, but I hate to send it in if there's another fix.
iBorg