here's one guy reporting something similar:
Fallout 3, Fallout New Vegas, Oblivion with Displaylink usb monitors - The Nexus Forums
And to Scoobz who really tried to help me the other night, I'm sorry I failed to report this installation. At the time, my external monitor wasn't hooked up and I never thought this thing could cause problems if I was playing right on the laptop screen...
FM