Resolution not adepting in Windows 7

Hey guys,

Ever since I'm using Windows 7 I'm having trouble getting the correct resolution for CrossFire.
In game I can pick different resolution in full screen or windowed mode. But nothing is changing after I save the settings. The game stays at 800*600px no matter what settings I choose. Kinda hard to play with when my main screen is at 1920*1080px.

To give you and idea of the problem:

(The wallpaper on the left is the secondary screen, don't bother it)

I tried:
- different detail settings
- different resolutions
- switch between windowed/full screen mode
- use secondary screen
- update gpu drivers
- update windows
- rebooting
- compatibility mode windows xp/vista
- run as administrator
- reconnecting monitor
- using different DVI port for monitor

Information:
- Using standard game launcher, no hacks, no custom skins etc
- No errors messages what so ever come up
- No special processes running (FireFox, Windows Live Messenger, TuneUp Utilities and AVG Internet Security apart from the standard processes)
Windows 7 Ultimate x64
4GB DDR2
Intel Core 2 Quad
GTX 275 - drivers: 196.21

Hope someone knows how to solve this issue...thanks in advance.
SickNature