Could be caused by lots of problem areas.
Are you sure there is no resource conflict? Look at the device manager in System - Control Panel.
Even if there is no warning, check if an IRQ is shared with other devices. And if so, try to force it to another IRQ (might even require moving PCI cards to other slots).
And did you check the Asus site for updates? Chipsets and state of the art devices like the Geforce might have problems with each other.
Waiting for an newer driver might also solve your problem...