I can confirm that the Vista and 8800GTX combination doesn't work very well with ArmA.
I bought the European 1.04 version, and I got lots of freezes and CTDs in the beginning. The main problem turned out to be related to my TrackIR4, so when I disabled that device and set my graphics settings to High (used to be Very High), everything went very smoothly and I only got the occational hang upon exiting the game. Â But I could always kill the ArmA process with the Task Manager.
Upgrading to 1.05 made everything worse, however. I got LOTS of crashes, both in-game and while loading a game. The textures were also sometimes corrupted, both in the 3D view and in the map view. Â But the biggest problem was that I couldn't activate the night vision goggles after I had loaded a saved game! Â This made it impossible to finish my current campaign mission.
So I had to switch back to a fresh 1.04 install, and everything was working much better (except for chopper control etc).
System:
Windows Vista Ultimate (32 bit)
nVidia 8800GTX (driver 100.65)
Athlon 64 X2 4800+
Asus A8R-MVP
2GB RAM