I had this problem with my DVR/dvd player. Try this! Shut down the unit first then unplug it from the outlet and wait a few minutes (make sure you wait at least 2 minutes) then plug back in, power on and try it. I know it sounds stupid but it worked for my dvd player. It would not read any discs old new or anything but now it is fine.
Good Luck
Also you may have an older unit and may need to look around for a firmware upgrade.
Phil, October 2007