Lumixan had that too when he got waayy to much demos inside his demo folder...
The game just crahsed too...
But i dont know if the crash then caused by some strange positions on maps or what else...
Because its very very very strange, that it crashed only when i got into water (example 2fort5) and not anywhere else...
And that because of too much data!
My paintball now works fine stable with fresh motionblur(1000fps)
Ive heard that problem a lot times and the demos are just filling up and up and up so it crashes after a variabl time depending on how much you donwload or record while playing...
Anyways its stable, its not your fault on B40!
I think that the quake2 engine got problems there...
I mean that engine is just about 14 or 15 years old and when quake2 released they didnt need 1Gb of gamedata!
Because my pball folder was about 1GB and maybe little bit higher! Now i got 800MB but thats still to big!
Maybe you can "fix" that or we just have to clean up our Paintball directory for stability and free diskspace! XD