the SHUDDER only happens on a few channels, most notably CBS, and only with fast action sports, namely the NCAA tournament, which was unwatchable. Turning the resoloution down on the DirecTV box to 720 totally fixed the problem. However, the picture was considerably duller, barely HD, so I put the box back on 1080i and connected the box directly to the TV, by-passing the AVR. There was still a hint of jerkiness but not nearly as much as going through the AVR. I reconnected through the AVR, this time just passing through the AVR without upscaling. It was almost exactly like connecting directly to the TV. The jerkiness was still detectable but greatly reduced.
I am willing to part with the TV if it's incompatible with the AVR or the DirectTV box. It's a Sharp 60" LCD. I got it on Black Friday for $799. The exact same model sells at BestBuy now for $1099, so I could probably get close to what I paid out of it, and then I could turn around and buy a Panasonic plasma. I have an old 50" 1080i Vizio in my bedroom, and it's as smooth as silk on the same channels.