did you try deleting your clientregistry.blob file in your steam directory? it will clear your steam config, and verify your game files. It takes about 10 minutes, whenever I have had any problems I do this and it usually fixes it.
If that doesnt work try to uninstall and reinstall steam.
I'm having issues with looping sound crashes. I'll be able to play fine for a bit, then it'll give me a loop crash that I can usually alt+tab out of and get back into game. But these crashes will increase in frequency until the game ultimately crashes solid and I'm forced a reboot. I've checked with the support help with valve and nothing they really give me works.
Win 7 Pro 32bit OS
AMD Athlon 64 3000+ 2.01ghz
2 gigs corsair ram
I use onboard sound, all drivers are up to date, I just did spyware/malware/virus scans. I'm not using an antivirus that'd hog pagedpool memory. And I don't think my pc is overheating, as a precaution I have both sides of my case off with a small house fan blowing on it.
I've turned down everything in the game visually and audio, and it still crashes. Might be time for a new pc, but that'll have to wait a few months. CSS has always worked fine, up until the orange box update. I've had problems with l4d and l4d2 and tf2 with these crashes, so I stopped playing them and just went back to css..now this.