I'm sorry to hear that you're having this issue.
You might try turning the AutoMotion Plus feature to either "Smooth" or the "Off" setting. To do this using your remote:
MENU > Picture > Picture Options [Enter} > Scroll to Auto Motion Plus [Enter] Choose OFF.
See if that, or a different setting in the Auto Motion Plus menu might help improve the picture playback.
I bought an LN46C630 a few weeks ago and I'm new to wide screen so this question may be attributable to my ignorance or an improper setting. I've noticed that on network programs (Comcast Cable) such as Seinfeld or old movies, the video frames seem to skip or move in a jerky motion on occasion (the audio seems to stay in sync). Can this be the tv refresh rate setting or something, or is it a result of the Comcast transmission? I don't recall ever seeing this with my old Sony analogue set. I'm surprised, and somewhat bewildered, at the number of settings and adjustments that are possible with this set. Thanks Bill