Left 4 Dead 2

Pre-ordered this game and all that, but kept getting this error at the demo. I thought it was something wrong with the demo and that it would be fixed when the real deal came out (like now), but I'm still getting it. Haven't been able to complete any levels yet because of it, I just start at the beginning of each level and maybe it'll last for a few checkpoints (longest I've gotten in one run is to the mall on the first level).

This is the only game this happens on. I've tried updating the Microsoft Visual and did a few 'verifying game files' on L4D2. Can anyone help me? Annoying to have bought a game that runs perfectly smooth on high when it just keeps crashing.

I've updated Steam a few times if that's what you mean. I've also contacted Steam Support but haven't gotten any answers yet.
It's boring not being able to play your new game. If this is Vista's fault, I swear to Lucifer...

Since I had the same problem on the demo and the real game, I think there's something with my computer. I'll try to download all of the new updates and if it still doesn't work, I'll reinstall L4D2. If I have to reinstall Steam... f*ck it. All of my other games work perfectly.