Originally posted by n00dle
It's probably due to the fact that HD tv's put image quality above image processing/scaling. This will cause fraction of a second of lag... over and over, which can and most likely will be quit noticeable on some tv's when you are playing time sensitive games such as FPS. If your tv has a "Game" mode, switch to that and it should help. The native display on HD tv's is a much higher resolution than on the older CRT tv's, and it may be scaling the image. Play around with your tv's display settings.