I was able to play the game for the first couple of days, 10 hours logged on steam, but all of a sudden every time I run BO2 (regardless of using GameBooster or not) the screen turns black and the loading mouse icon comes up, before it turns back into a mouse icon. I have to CTRL+ALT+DEL to get out of it, and it says "Black Ops 2 multiplayer has stopped working".
I'm using a Lenovo G570, and I've updated all drivers and validated my steam game files, disabled steam sync, changed dates/timezones, etc
Any ideas?