Can you post a pic of this line you're referring to? Are you using a software or hardware player to play the videos? If it's a software one, which one are you using? Also what res are you trying to play them at?
Ill post a picture tomorrow. I have the "line" when the camera is panning in VLC, GOM or the HP DVD players. The resolution of the screen is 2560x1440. I only get the line when the videos are in Full screen even if they arent 2560x1440 (obviously). It may be normal btw.