That is an issue I have with RtCW over many years. In my testing it isn't video - it's the particular sound card I'm using. Disabling sound completely (s_initsound 0 in game etc), and unloading all snd_ kernel modules sometimes gets me past the occasions where flamethrower is used. The other game which does the same thing is Q3A (RtCW's base engine) binary version (not IOQuake). Playing on an old SBLive sound card (emu10k1 driver) there are no problems, I suspect because it is on this list.