Nvidia and Samsung! Please help!

I have a Samsung lns5296dx (52 inch, 1080p) and I've hooked my Vista desktop up to it, which has a NVIDIA GeForce 6150LE. I had someone set it up so that it would be an unstretched full screen desktop. I believe he set a custom resolution at 1920x1080 (which is that Samsung's native resolution).

However, somehow the custom resolution setting got removed and I can't get it back. When I enter a custom resolution of 1920x1080 and click "test" it just reverts back to 800x600 and doesn't recognize the newly created custom resolution. Does the NVIDIA card not recognize this resolution?

Right now, the highest resolution that works is 1280x1024, however the image is stretched. If I change the samsung to 4:3, it works, but is obviously a smaller image.

Any ideas?

Thanks,
Kyle