I have the same problem, I use Win 2K, Geforce 4 (any drivers, makes no difference) and it locks, I've found the best

way to do it is through editing the ini file that has the graphics details set in it (UnrealTournament.ini)
[WinDrv.WindowsClient]
WindowedViewportX=1280
WindowedViewportY=960
WindowedColorBits=32
FullscreenViewportX=1024
FullscreenViewportY=768
FullscreenColorBits=16
Just change the above things for the resolution/depth you want in windowed and fullscreen mode and you should be fine (just make sure you go for the standard numbers

)
***DISCLAIMER*** Back up any files before editing, the author of this thread cannot be held responsible to any things that get messed up on your computer through this advice