Steam and Win7 just generally don't get along that well. Hopefully steam and it's (almost weekly) updates will pinpoint the errors and fix this. I have had issues launching and playing steam games every since my install of Win7ult64. Usually the game will play for a short bit and crash given the "hl2.exe has caused an error" or "___.exe has stopped working" etc etc. Originally, I couldn't launch Counter Strike Source in 1920x1080--I had to manually lower my resolution on my desktop, and unplug my second monitor. Then, and only then, would it launch. VERY frustrating to troubleshoot these errors.