Another PC to HDTV question...

I have a PC with an Nvidia 6800 GT card, and a Samsung 67" DLP TV with a PC video input. When I hook them up, it works almost flawlessly, except I get this horizontal banding that goes across the TV, which speeds up or slows down depending on what refresh rate I use. Even when I use the optimum settings in the manual, it still shows, and each game I play seems to change the refresh rate on it's own, so each one has various degrees of banding. I should also point out that I'm using three 6' monitor cable adaptors to connect them, since the components are pretty far apart. Any ideas on what would cause this banding effect? Should I try connecting them a different way?