its not a driver bug, otherwise tons of people would be experiencing it.
have u set the settings:
in the counterstrike config (or type it in console)
Truform will kill performance so u make sure its off.
Its likely you're system isnt working nicely together (it happens).
And as a last resort, you are to reformat.
Nvidia drivers and ATI drivers do NOT get along. If you switched u have to make sure EVERY BIT of nvidia driver trace is GONE. anything remaining is likely to cause an issue (although in some instances its totally random)
All your hardware drivers and stuff should be updated to the ABSOLUTE latest revisions. New stuff tend to have fixes to compatibility issues.