Star Wolves 3, random bluescreen

[SanLiet]

Hi,
I have a problem with Star Wolves 3 (Steam edition). It looks like a software problem, but I'm not sure.
The game crashes to a bluescreen after a random time playing (anywhere from 10 minutes to 3 hours), the only hint I have is the bluescreen. It says, the Nvidia Desktop Manager DLL caused a problem.

System Specs:
Windows 7 Home Premium (newest patches)
Intel Quad Core 9650
Nvidia GeForce 8800 Ultra (Driver 196.21)
Dual monitor (24" HP, 20" Samsung, both connected with DVI)

If I switch off/deactivate the second monitor (Samsung) for my system, the game runs always longer before crashing.
After the bluescreen, I have to reinstall the Nvidia driver anew, else I get the crash right after loading an existing game or starting a new one.
I tried the newest driver for the graphicscard and also the previous versions but without success..

Any tips/hints/help/brainfood?
I'm a little helpless here

PS:
Other games (i.e. Empire Total War, Nexus: Jupiter Incident, Dawn of War 2, ...) run smoothly for hours wihtout crashing. Temperatures for the CPU never goes over 55°C and the GPU also never goes higher as 60°C, even when crashing..