SushiForYou

I had this same problem as well. Just that it didn't say it was illegal or anything. This was really annoying for my brother b/c he bought ARMA 2 CO just for this mod only to find out that we couldn't play together. I'm about to try out what blockhead posted and hopefully it works. EDIT: I just tried to specify the client ports on both of our steam games and we launched it and tried to join the same server but we still couldn't play together. I hope there's a solution to this :(