It is not your HDTV, it is the show that is on the channel at the time.
I noticed this when I was on Charter Cable, when I got my new Samsung HDTV. Everything was wonderful, unless I turned to TNT and an old episode of Law and Order was playing. Everytime the show panned left or right, it was like it was "stuttering"...a herky jerky motion that drove me nuts.
I thought, great, I bought a LCD that can't process this stuff. But, it wasn't my TV. It is the way that some broadcasting companies compress/encode their shows.
To make yourself feel better, turn to HDNet, or something that you know broadcasts true HD all the time...try ESPN. There you will notice that everything is just fine.
So, relax, and if you feel up to it, send the broadcasters a nasty note telling them...if you want to broadcast HD, then broadcast HD...enough of this stuttering crap!
I've also noticed that some go the "fish eye" route, where the center is clear, but the sides are stretched and when they pan, it takes me back to some good drinking binges in college.