Same problem after formatting
I tried all the things you suggest me (clean boot and unplug secondary monitor), but the problem remains the same even now that I formatted the system.
In these days after a disk change windows refuses to startup, so I formated and reinstalled the system (still windows 7 64bit sp1) and downloaded a fresh copy of TWD from steam and latest Nvidia driver, but I have the same problems.
The game after a while try to reinitialize the graphic card and than crash to desktop with the error "Walkingdead101.exe has stopped working".
I think it's a problem of compatibility with my graphic card (NVDIA 9800GT) and the developers should make a fix for this.