It almost sounds as if the picture was knocked out of alignment. Assuming all of your inputs are different and that it's not a cable issue, it may be remedied by a simple adjustment, however it will likely require a technician.
I have a Samsung 50" led DLP, the HL-T5087S, to be exact. I have a Sony PS3 80gb as my blue ray player, and am running an HDMI cable straight from the PS3 to the TV.
I bought Transformers 2, and noticed a bright blue/white line across the bottom of the screen, slightly wider on the bottom right. It was there the entire time, on the menu screen and the black widescreen bar. I hadn't noticed it before, so I also tried my copy of the The Watchmen, and the line was still there. Not as wide, and more white than blue, but still present.
The line is not there when watching hi def channel through dish network, playing PS3 games, watching standard DVD's, or standard def TV channels.
To be honest, I am not sure if this is a problem with my PS3, the TV, or possibly the cables, but thought I would start here.
Thanks for any help that you can provide.