Lawman, ultramon is still not 100% steady with Vista. I can attest to this, using it all day at work (where I am still at this moment).
Therefore I would suggest trying a combination of things (such as turning off Ultra-mon during gaming and turning off the second display) and see if this works. I have noticed some minor quirks where Ultramon's desktop settings would sometimes not take effect, say after I unlocked my setup, and would default to a single monitor when waking up from sleep.
Neither symptom was exhibited with Windows Desktop Management, but then I didn't have the useful taskbar features of Ultramon available
If you are gaming on a multi-display setup, I highly recommend turning off the second display before gaming because you are always going to notice quirks with certain games. This is why I no longer run a dual-display configuration at home on my entertainment system, it simply has too many issues, mainly because of the way games and game engines are designed.
Try these 2 things before messing around too much with video drivers and you should be good to go.