I've got a very weird issue involving a display problem on my secondary TV on a Dish network 722K.
Let's get the equipment out of the way first.
Main Tv: Samsung 67A750 DLP connected via HDMI
Secondary TV: Panasonic TC-P42X1 Plasma connected via component/Coax
Reciever: Dish Network 722K

When I added the Panasonic to the bedroom, I used the standard Coaxial cable from the 722K which sends a standard def signal.
Yesterday, I ran a 50' Component/RCA audio cable from the 722K to the Panasonic. It worked like a charm, sharing the HD feed between the Panasonic via component, and the Samsung via HDMI.
today, when I turned the Panny on, I got purple and green lines scrolling up through the picture and horrible buzzing from the audio.

I tried reseating the cables, no luck.
Tried the other component inputs on the Panny, no luck.
Tried a spare 50' cable, no luck.
Tried my LG DVD player, with the cables, which worked fine.
Tried my Panny blu-Ray player with the cables, worked fine.
I even tried connecting the spare 50' cable to the first (Which runs through the attic and into the bedroom), and then running it back to the Samsung.
Got a perfect picture.

So, this all seems to rule out:
Bad cable? No, works fine going to the Samsung. Plus, the spare cable delivered the same poor result.
Bad inputs on the Panny? No, other components deliver a fine picture.
Bad output on the Dish 722K? No, outputs fine to the Samsung DLP.

This setup all worked fine most of yesterday and this morning.
no other components have been added anywhere. I've tried turning off all other devices in the house. THe SD feed is still fine.
I'm completely baffled???