I have a 1.8 core duo macbook, which previously had a CD-RW drive that stopped reading audio CDs, so I had it replaced under my warranty at John Lewis. It was replaced with a MATSHITA DVD-R UJ-857 and I got it back yesterday, so I was pretty happy that I can now burn DVDs. Only problem is, I just found out that I can't burn CDs with this new drive! When I try and burn a disc using iTunes or Burn, it comes up with an error message saying 'The device failed to calibrate the laser power level for this media' I have tried different discs, nothing works, even when I reinsert them several times. Any ideas as to what the problem is?