I'm using a Panasonic Blue Ray player with a Samsung LCD TV. I have an HDMI cable between the player and the TV.
I haven't watched a Blue Ray Disc with it either, but I've never seen what you describe with a DVD.
I'd try another player.

Picture should not a a line down the middle of the screen when watching anything. It sounds to me like a bad player.

Are you sure it's connected correctly?

does the set have multiple co-ax inputs? my new panasonic plasma does not. it would be nice to use a cable splitter and have a box input and straight cable input and switch between the 2 feeds. but you will get a hd cable box soon so why bother? i had a hd set 10 yrs ago and did not get a dvd unit for 1 year. duh. what was i waiting for? took me 2 more years for cable hd to show up.

Should not have a line no matter what kind of disc it is unless there is either a problem with the player or a bad disc. If it does it on all discs then it is a player problem.

Upgrading the cable to hd will definitely give a much better picture. It will not affect the blu ray though. For best pic both should be hooked up via HDMI cable.