I am experiencing freezes during my play of single player Left 4 Dead. I heard if you type mat_queue_mode 0 in console it may be fixed. I was wondering what exactly should be typed to do this as I keep getting the message 'unknown command' and stuff.

Further, what more could be causing the freezes including the sound loops. I already put Shaders down as I read somewhere else in a topic here that the Shaders can cause the freezes too (have them on low).

My rig is strong;

Asus P5E X38
XFX GTX260 XXX
OCZ 1150RPR CAS4
Xilence 700W
Intel Core2Duo E8400 @ 3,0 GHz