Manually rewind (or fast forward, whichever will get the wrinkled section away from the playhead) to as far as it will go the other way. MAKE SURE THE TAPE IS STRAIGHT, AND NOT FOLDED ANYWHERE!!!!!
Then, using the camera, fast-forward (or rewind, whichever will take the wrinkled section through the playhead) all the way to the other end of the tape.
Do that a few times. It should straighten out the tape enough to play it. I've done that with a VHS tape (successfully), and it should work with any cassette tape.
AMD Sempron 2600+ (Socket 754; 1.6GHz)
768MB Crucial PC2100 (I know, I really need PC3200 :()
ATI Radeon 9200