Most puzzling driver issue I have ever encountered

Hello everyone.
I am graduate student running a vista 64 business edition (got it from my university) computer with a Q6600 and an ASUS 4850 video card. I have been trying to run the modeling software COMSOL, and it works fine until I try to view results i.e. graphically intensive things. Upon viewing results the program CTD and spits out an error log. When researching the error log, it suggests the problem is with me using dual monitors. So i switch off dual monitors and COMSOL still doesn't doesn't work. So next I rolled back the drivers and tried again. This time COMSOL works perfectly. I restart the computer and suddenly COMSOL doesn't work with the rolled back drivers. So I reinstall the new drivers and COMSOL works again, with dual monitors and everything else. I restart the computer again and COMSOL doesn't work. I have tried this a few times and it seems whenever a driver change is made on the computer, COMSOL works, but then when the computer is restarted something happens that causes COMSOL to stop working. Does anyone have any idea on what may be causing this?

-Dazed and confused