It sounds as if the DVD portion of the combo player isn't playing correctly. If it says that it specifically can't play the disc, then that error is coming from the combo unit, and not the television.
You may want to get your VCR/DVD combo unit serviced through the manufacturer.
samsung series 5 tv won't play dvd from my panasonic vcr-dvd. The dvd player keeps recyclcling and comes up with cannot play this disk. The vcr side works fine. When I hookup a seperate sony dvd player it plays the disk fine.