What kind of TV is it? LCD? 120Hz LCD? Plasma?
And what sources are you seeing it on? DVD? Blu-Ray? Streaming?
My new Blu-Ray player occasionally shows blockiness during action sequences and some jerkiness in people's movement at other times. It's not a lot but enough to be noticeable. Is this normal behavior? I know the player is moving a lot of data over the cable and into the TV. I have a thick, high-quality Sony HDMI cable between the TV and the player. This is the second cable and it's not resolved the problem. Is it likely to be the player, the cable, or the TV?