You could have some interference from some analog cables. I had a similar problem with my old CRT tv and my 360. I used the component inputs and the S-video input at the same time. I always had something similar to what you had and lines that would travel up the screen. Unplugged the S-video without thought and it worked.
If its not the cable interferring, it might be some shielding within in your tv. Just IMO
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