I believe the problem is the resolution, the TV may not be able to take 1080i, the Tivo is currently set to. Try a lower resolution, like 720p, or 480i.
Some TVs do strange things when it receives a resolution it can't handle.
What model Series 3 do you have? Is there a format button on the front? Press it a few times.
Series 2 (PLS, sold)
TiVo HD 1TB (157 HD Hrs, PLS, "652")
Roamio! Oh, wait, Its Juliet!
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!