Ticking/Popping sound with HD Tivo

I have a new TivoHD using basic cable (analog and some local digital/HD). Fox (Analog) has a distinct ticking sound in the background. It is very noticeable once your ears adjust to it. One of the other channels also ticks, but there is an HD version of that channel that I can tune that doesn't.

Anybody else heard of anything like this? It did not happen with my old Series 2 with RCA cables for the sound..