Your video card, a renamed GeForceFX 5900 Ultra, is unsupported. I'm not sure where you saw it was 'mid rated' but it is not going to work for GRAW. A GeForce 6xxx/7xxx series video card, or ATI 9600/up is required.
States it right here:
http://forums.ubi.com/groupee/forums/a/tpc...13/m/6651020414
MID-RANGE These cards are Enough powerfull to provide you fairly good experience
* Radeon X1300 (All-in-Wonder 2006)
* GeForce FX 5800
* Radeon 9700
* GeForce PCX 5900
* Radeon 9800
* S3 Chrome 27
* GeForce 6600
* Radeon X1300pro
* Radeon 9700pro
* GeForce 5800
* GeForce FX 5900ultra
* Radeon 9800pro
* Radeon X700
* GeForce FX 5950ultra
* Radeon X700pro
* GeForce 6800LE
* GeForce 6800XT
* GeForce 6800 (PCI-express version)
* GeForce 6600GT
* Radeon X800SE
* Radeon 9800XT
* Radeon X800GT
I have the 5950 and I am having the same problems. Oh well, I got to wait until January when direct X 10 cards are out.