Hi zero hour,
You seem like you know what your talking about and I was hoping you might be able to give my problem a try.
I have l4d2 installed on windows 7 32 bit. It had been running perfectly for quite some time until a few weeks ago when it started crashing whenever I got into gameplay. I tried your fix but unfortunately no luck.
The crash happens the same way every time. I start l4d2, the opening cinematic and the menu interface work perfectly. I join a lobby and again everything is normal. The level/server loads and the opening cinematic renders perfectly. Everything continues as always except that once the game goes into gameplay (first person), the game shuts down immediately and goes directly back to windows. There is no lagging of any kind, the game simply turns off and returns to windows.
Now after reading some articles and posts on the internet, some people think it may be a hardware issue. However, I am still able to run Day of Defeat perfectly while simultaneously running a movie on my second screen. To me this would indicate that my computer hardware is not the problem. Presumably if it were a hardware issue my computer would not be able to handle other similar tasks.
I have checked my graphics cards settings and all of the settings are on default. I'm stumped and I would love if you could give me a hand.
One final note, I pre-purchased the game and on the night it was released there was issues with running it. Someone posted a quick fix by changing the name of a file. I used it and the game worked fine. Not sure if my problems are related to that but i thought I would give you all the relevant information.
Thanks for your consideration