It's likely that your aspect ratio in the cable/sat box is off, or that you have a ZOOM feature enabled. You might try calling your cable/sat company to see if they can walk you through setting up a 16x9 aspect ratio.
Once that's completed, make sure that you don't have a zoom feature enabled in the television. There are two parts to this equation - the source and the television, so both have to be on the right setting to properly fill the screen to see the picture as it was transmitted.
Hi Folks. I purchased a Samsung 640 two months ago. Love the TV, BUT on many of my HD Channels (Comcast) the picture is cut off. Things like titles and channel logos are cut off on most channels. That said, most of the big network channels (FOX, NBC...), fit the screen with not problem. Any ideas?