My MacPro (early 2008) has had this problem for a long time. Apple doesn't have a clue. When I restart, the DVD tray opens and closes normally. But after about 15 minutes of running the tray no longer responds to the eject key or any other eject command. If I restart it works again for another 15 minutes. I installed Snow Leopard on a clean drive, at Apple's suggestion. Didn't help. Anybody have any thoughts?