n-Vi stops reading disc after 20 minutes

Recently my n-Vi stops reading discs (both CD and DVD) after about 20 minutes of play. When I try to change tracks, the screen shows it jumping to that track, but freezes it at the same location. For example, if it stopped at 2:48 minutes into track 9, when I forward it to track 10, the screen shows track 10, time 2:48, but it would not play. When I switch off the unit and restart, it would say "no disc". The only way to get it to play again is to switch off the machine for an hour or so. Then it can play again, but freezes after another 20 or so minutes of play.

Has anyone experienced this problem? Is it just a firm ware issue or it's something more serious?