I second the trying different drives or different PCs. I have 3 CD/DVD drives in my PC (from upgrades that I just add instead of replace for some silly reason) and find some discs won't work on some drives. Has nothing to do with brand of CD-R or application used burning that I can discern. I've had some CDs I coulnd't drag and drop from (hangs up with 99 days left to finish copying) and found that if I used Clone CD or Roxio EZ CD Creator Copy Disc funtion, it would work and I could read off the new disc no problem. Logical? No...but somehow it works. You might want to give that a try.
On the flip side I get a lot of DVDs that I cannot copy with Clone DVD because I get a packet error....but I can drag and drop the files to my HD and then burn with Clone DVD no problem.