Hi,
If the tray of the drive is obstructed sometime this problem can occur. Make sure the tray is able to open to its fullest extent and there is nothing in the way as it opens.
Also applications running on you PC might try and close the tray if they need to access data from the disk. You can bypass the operating system by placing the ROM BIOS setup and then seeing if the tray opens and closed on command on the eject/load button.
Andy
June 2006