nzone.com are reporting that the latest 169.28 beta ForceWare drivers for Windows XP 32-bit, Windows Vista 32-bit, and Windows Vista 64-bit nvidia NVidia video card users have been released. These specifically address some issues experienced with ut3 UT3.
"ForceWare Beta Release 169.28 is provided below for customers experiencing issues with the retail version of Unreal Tournament 3. This driver is only recommended as an update for these customers. All other customers are recommended to use the latest WHQL or Beta drivers offered on NVIDIA.com."
US Driver (version 169.28)
Windows Vista 32-bit (36 MB)
Windows Vista 64-bit (49 MB)
Windows XP 32-bit (39 MB)

International Driver (version 169.28)
Windows Vista 32-bit (71 MB)
Windows Vista 64-bit (58 MB)
Windows XP 32-bit (70 MB)

Source: beyondunreal.com