Red and green horizontal lines migrating on screen


I have red and green horizontal lines migrating from bottom to top of my screen. I have an HT300+ projector. They vary in brightness and occur intermittently. I notice them more in the evening. They occur when watching TV or dvd programming.
jlettire
I have read of a similar problem mentioned on Avsforum.com regarding front projectors. The concensus there was that it is caused by a ground loop problem, most likely coming from your tv cable.