I posted this as a support ticket as well.
Hello, i have a community account on steam that has ArmA II: Combined Operations.
We got this account so we could play the DayZ mod that has recently been released for the game. We had multiple people get on the account to play it when it was available.
Recently those people that played on the community account all purchased Combined Operations for their own, on their own steam accounts.
Now, when we all try to join the same server, the community account isn't able to play on the same server, it says "You were kicked off the game" or "CD Key invalid" which makes no sense because the games were purchased direct from Steam.
We feel this is an ArmA problem and not a steam problem, because we were able to play other games with each other, but when we try to play ArmA II with each other it gives us those errors.
We've all tried reinstalling our games and also tried deleting all profiles on each account (in game as well as in Documents/ArmA II and Documents/ArmA II Other Profiles.