here is a shot in the dark.. try turning motion blur and shadows and shaders off/low setting
at least this helped me to have alot less crashes and made the death valley map slightly laggy instead of a slideshow.....
also is your graphics card drivers updated? it might be the older drivers work better OR there are new drivers that make the game run smoother.(BE CAREFUL make sure its the correct one,
this can go really bad if it doesn't go right)
is your audio drivers updated? new audio drivers might get rid of stutters and crashes. (BE CAREFUL make sure its the correct one, this can go really bad if it doesn't go right)
also there is options in the control consle in game to adjust for multicore set ups.
clear your shaders in your temp file (info on how to do this is around here on the board some where)
play servers with a ping of 60 to 90, 150 max ping is the limit for me.
just start with small adjustments first ...hope this info helps ...
(disclamer.. loading or doing a audio/video card roll back on the drivers are at your own risk.)