Naiko N1003 No Disc Message?

My 15" LCD TV/DVD/Monitor N1003 has suddenly (i.e. within the last 12 hours) come up with a message every time I try to play a DVD that says simply "No Disc". I can't find the manual and have no idea how to fix it. I have tried several different DVDs from 2 regions, but not had any success in solving the problem. Does anyone know how to repair it? Or has my faithful little TV/DVD combo bitten the dust?