how to remove video noise on my plasma? DESPERATE

I have had this exact issue several times, and each time it was solved by tightening the coaxial connection at every connector...wall, cable box, TV, and including the connections outside (splitters, etc).

I'd try this first.

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.