Was listening to a CD when it started skipping and then stopped playing - I went to eject and kept getting a flashing "error 4" message - it won't let me eject, play or switch to a new cd - any clues on how to fix?

 

i kept playing around with the power of the unit and hitting eject at the same time and some frustrating banging on it might have helped also....by the way this is my second unit and it does the same thing they said it wouldnt do so I am switching it out for another unit before it completely stops. I cant be without music