This could have somethin to do with your RAM
Either you dont have enough RAM, or you have to many progs runnin while you play cs.
So I see 2 solutions ; Close all useless progs so you can get the most out of your RAM. (try scanning for Mal/spy/ad/ware on your comp, those take a lot of memory)
If it doesnt help ; Go to your CZ Launch Options : Games -> Right-Click on CZ -> Properties -> Set Launch Options ...
Type in either : "-heapsize #" or "-zone #"
where # should be, maximum, half of your RAM, so if you have 512, type in : "-heapsize 256000" or "-zone 256000" since its bytes and not Mbytes..
Pretty much all I can suggest, it could be anything else from a bad driver to hardware malfunction.