This guide will also solve the errors such as
When I join the server I get kicked back to the lobby without any error messages
Launch Operation Arrowhead from steam and select the option to re-install BattlEye Anti-Cheat client. If you are using retail download the latest version form http://www.battleye.com/download.html and put it in a folder named ”BattlEye” in the “Expansion” folder of your Arma2:OA main directory.
