I have a slot loading Imac DV and the disc drive wont work, with a catch... Audio CD's work fine but software CD's and DVD's either return the message "this disk is unreadable..." or nothing happens and the disk pops right back out. I have tried a few simple things like trashing the CD/DVD preferences and disabling the drivers extension but nothing has worked. The computer will not start up from the system CD either. Is the drive toast and if so why do audio CD's work. Please help. Thanks 