Twice I've had a strange problem come up. Ignore the box for a few days, turn it on, and have audio but no video on any channel. The OSD is very dark (like the brightness was turned down) but usable.
Kitty, this is a long-shot. By chance is it cold in that room? My 32' RCA did that when the room was below say 45 degrees. (I forget the exact temp) Even colder and it would not turn on at all until the room was warm. I discovered that before moving in permanently. I'd set the heat just high enough to keep the pipes from freezing until I came back to work again.
When ever I tried to turn the tv on before it was warm enough... it was a PITA to get it working again. Would have to unplug it and restart several times to get it to function AFTER the room was warm. One time I thought the tv was ruined.
That was back before I had an FTA receiver, only OTA. So it was only tv related.