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After doing some research, I have the following command line args:

+mat_forcehardwaresync 0 +snd_async_prefetch_priority 1 -heapsize 1024000 -dxlevel 80 -width 800 -height 600 +cl_drawmonitors 0 +r_shadowrendertotexture 0

This gives me DX8, stable saving and only rare crashes. Now if only I could get the multiplayer to work...
 
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