does this problem occur if you hook up any other video game systems or dvd players, etc... into that same source input?
I have a tv that is like that. It is old and only has one a/v input, which causes erratic problems with my picture quality when I have my xbox plugged in.
My suggestion is to try another device in the same input (i.e. video 3 or video 4 or whatever). There may just be a problem with one source.
Let me know if what I said is confusing