Radeon 5870 isn't displaying HDTV Quality Properly

First of all, some info about the rig;

- Asus Rampge Extreme II Mobo
- 650W PSU
- ATI Radeon 5870 HD GFX Card
- Intel i7 920
- 6GB RAM

And the monitor I am using is a samsung P2470HD.

I am trying to use the HDMI output of the graphics card into the TV, however when I set the resoluton to 1920x1080, the picture becomes horribly distort, there is a 1inch border on all four sides of the screen and it generally looks a mess!

However if I take the resolution down to 1680x1050 it is fine. It also breaks when I set the resolution to 1776x1000.

Any help would be appreciated! I have already tried the obvious, turn it on & off, re-install drivers etc etc.