I, too, have been experiencing this problem only recently. I'm afraid I'm nowhere near the tech-savvy human you appear to be but I do know the following: I'm running Windows Vista 64 (Service Pack 2), Dual-core 2.5 GHz processor with 6GB RAM. It only happens on L4D2 and only in the past couple weeks. Something that happens that isn't mentioned above is that my computer monitor goes to sleep as if the CPU is shut down - but it's still on, looping the last bit of sound, until I hold the power button down and manually reboot. I did notice that the two times it happened last time were 11:00pm and 1:00am on the dot but then it happened later, around 1:45am.
I'll try that sfc /scannow bit and get back to ya'll. Thanks a ton!
EDIT: Just tried and noticed this message a the top of the prompt window, which doesn't ring a bell: "c:\Users\Owner\AppData\Local\Msyitwgeawcb.exe is not recognized as an internal or external command" if that helps any.
Moderator edit: Moved from the Windows 7 forum to a more appropriate forum
Edited by rotor123, 18 January 2014 - 12:22 PM.