Sorry if this is in the wrong place, I wasn't sure which board I should post this on.

There are very faint "lines" that move across my screen when my cable box is outputting 1080i. Outputting in 720p makes the lines go away. They aren't THAT bad, but are visible especially when the picture is dark.

If the screen were a compass, the lines go from northwest to southeast, and travel towards the southwest.

When watching DVDs or being on any other input, the lines don't show up. I don't have any other components that can output 1080i to test if it's something wrong with the tv.

Any ideas? Is this a ground loop? Why would it go away on 720p?

Groundloops do not travel in that direction.

I have the same problem.

Comcast component to Yammy reciever and then component to projector.

I'm wondering if maybe I need one of those 'clean power' strips or some kind of interference/noise filter?

I also have this problem running through a Yamaha receiver, although I'm outputting from 720p at all times. Going to just run HDMI directly to the TV and audio to the receiver to fix, probably easier than diagnosing the interference!