svideo cable noise supressor

I'm trying to gather information in order to build a supressor for the (mains) noise that appears in a svideo cable conection I have between My PC and TV. I get light shaded and light hilighted horizontal bars, about 50 lines thick scrooling in the TV.
I'm thinking about a passive filter tuned to High Pass 50hz, but I'm afraid I'l break the sync signal.

Suggestions, schematics, flames, horror stories anyone ?

-Miguel

My opinion: this is a ground-loop probleme.