for anyone who might care, my issue is resolved: brought it in to the apple store genius bar, turns out an internal part in the optical drive had come loose and was blocking the pathway. had to replace the optical drive...however, it also turns out i was still covered by applecare, so no charge (instead of $151)! i got my MBP in 2009, thought i'd gotten one-year coverage but apparently i got the three-year package, woohoo!