Doug,
The buzz doesn't stop with any input change, the sound is like there are bees in the tweeters, as the volume is increased the buzz doesn't get any louder. It's not apparent unless the volume is way down to the point where the TV can barely be heard.
It's not a major problem as far as listening to stuff, but as far as i know that sound shouldn't be there.

A computer once beat me at chess, but it was no match for me at kick boxing.