I had a similar thing happen to me at the weekend, i had the tape adapter that i use for my ipod get stuck inside my radio.
The problem with mine was that the thin cable that runs from the cassette got lodged underneath and jammed it. The motor was trying to eject the cassette but couldn't.
I turned off the stereo and managed to free the cabe, turned the stereo back on and out it popped
hope it helps