Not much help I know, but I get exactly the same problem running Unreal Tournament (W2K/Build 2195 & Matrox G400 drivers for W2K v5.00.07). It only locks up when running full screen though, works fine in a window. Appears to be something in the G400 drivers ?
I run W2K on a Dual Celeron/BP6 board, you running single or multi-processor ?