I happen to have one of these myself, have used it daily for nearly ten years without a problem, for what that's worth. The only thing I can suggest is try resetting the player. To do this, press and hold the stop button while pressing the power on button. If that doesn't work, most likely the disc transport may have gone bad. A new transport can be put in for around $150, it's your call if you want to spend that much on that old a player.
Best of luck,
Dan
Best of luck,
Dan