I've been trying to troubleshoot this issue, but so far no luck. I have a series 2 Tivo 54040 that's about 4 years old. Recently it's started to misbehave in the following way.

Video is intermittent - approx. 1 sec on/ 1 sec off - and there's no audio on live tv. Recent recordings are grey without audio. Menus work but are also affected by the video on/off phenomenon. When I remove the source (RF in or S-video in), menus are stable. Both video and audio are fine on old recordings.

I rebooted the unit, but the symptoms remain. I appreciate any pointers to a solution.