Try cleaning the lazer. Where the tray goes into the unit, you will find a small lens, that is the eye that reads the info on the disc.
Turn off, unplug, and dissassemble the unit, probably just the top cover. Find out if the lens is visible. If it is good, if not try to wind the motor that feeeds the tray gearing to open the drawer, and this should access the lens.
Then for the cleaning part, simply use a cotton bud. Breathe on one end of it, and gently wipe the laser. Then turn the bud over and use the dry end to wipe again.
Frequently cures the problem, as dust is drawn into the machine when the drawer is opened and settles on tthe laser.
Put it all back together, hopefully it will ork.
Good luck.
Sid
December 2008