I assume you aren't getting the infamous ERR3 code or any other error code. Try the following reset procedure originally posted by Tone - I know it sounds like mumbo-jumbo but it works!

Disconnect the negative battery cable. Depress the eject button 50 times,
turn the key on and depress the brake, turn the key off and reconnect the battery cable.
The lights on the CD changer will flash orange-green. As soon as this stops,
depress the Eject button. This may release (eject) the CDs.