One particular batch of my backup DVDs no longer read. They were written on a dual 800 with it's original built in superdrive. This superdrive broke a few months ago and was replaced. Now none of them will read in that mac or my other mac (dual 1.4). It just spits them out. I have no other read/write DVD problems and the batch in question has worked OK many times in the past. Anyone know if there is an issue with older superdrives or if there is a way to bring them back to life?