Lots of people have had that problem. Search: "video hum" , "ground loop" , "isolation transformer".
I'm guessing the problem is the patch panel.
Eliminating the culprit equipment is the "best" way to eliminate it, but often impractical. An isolation transformer can eliminate the problem.
(don't ask me where to buy... I dunno yet... I'll be buying one soon... I get this from my cable box)