RCA Direct TV DVR 40gb pixelates, looses signal on... (by 2 users)

On my above model dvr, one tuner on certain channels only has intermittant signal loss. Sometimes programs are unwatchable. I can switch tuners and go to the same channel and it is fine. When you go to that tuner in the sat signal strength meter, it will be 90+ but for a blip will be 0. I can switch cables on the back of the box but it doesn't change, it stays on the same tuner (cables, lnb eliminated).