i have the exact same problem. I also can launch Arma 2: OA perfectly, but when I try to launch Arma II it says that bad serial was given upon setup. I bought Arma II Combined Operations over steam. Edit: When I try to open Arma II Combined Operations over steam, nothing happens. And when I try to open Arma 2: OA it says: "Error creating Direct3D 9 Graphical engine" I can open DayZ, but when I try to play on a server it says "You cannot play/edit this mission; it is dependent on downloadable content that has been deleted.Chernarus". I have the beta patch 94876