It might load 1 out of 20 tries. This is the error I get:

nexuiz-linux-686-sdl: radeon_dma.c:210: radeonRefillCurrentDmaRegion: Assertion `dma_bo->bo->cref == 1' failed.
Aborted

Could you give us some details about your system? This looks graphics related so what OS are you running, what drivers are you using and what graphics card do you have?

It might be worth loading the 'low' graphics setting and retrying. Then incrementally try switching things on and seeing if it makes a difference.