DVR no longer records properly

DVR:  Scientific Atlanta   Explorer 8300HD

Problem:  DVR starts recording, then stops immediately.   On playback, only 1 minute duration is indicated, and error message displays "We're sorry, this show is unavailable."        Most recordings are the same with 2 exceptions.   I think that those two were watched at the same time as being recorded.   

I have unplugged the DVR twice and rebooted; with no improvement.