midget2short2c

I just bought Arma 2 for my self and one of my friends and my copy of Arma 2 will not let me play multiplayer I can download the missions and I can see all of the servers, but the second I try to join a server it will download the mission information then boot me right back to the server browser. the same thing happened to my friend. I gave him my old one I bought both of them on the same day. I gave him my old copy because I was getting an invalid CD key error on every server I would try to join. even if I would try to host my own, But I purchased the game. please help me fix this problem..