how to remove video noise on my plasma? DESPERATE

If you're not getting audible "hum" as well, then I doubt it's 60 cycle emf. It sounds (looks?) more like RFI which might be coming from a digital device.

Also, I understand it's not cool to put a CATV isolator (like the ones sold by Audio advisor) on your incoming cable if you're getting digital channels, because it screws them up.

Try unplugging all digital devices except your cable box (especially DACs and computers,) and see if that doesn't help.

In my experience this IS video noise from a ground loop. Tvad's solution may help if you are not getting a good ground because your connections are loose. Try an isolation transformer on the co-ax from your cable. If that works you know the problem; not sure about the solution if you have digital cable.

Swamp, how can we find out how isolate our system ground from the cable company without messing up digital channel reception? I could write to whoever makes the current crop of isolators and ask them (follow the money, which they're about to loose, right?) but I don't know who they are (I've always made my own ;~))

"It's always something . . . . " Gilda Radner

Buy yourself a cheater plug from the hardware store.
First try it on your cable box or whatever you are using to send the picture to the tv. If that doesn't work try putting it on the tv itself.