Marbo13

I have the problem, that after i started Arma 2 today i got the Problem, that the came a message cd-key in use. Now my Question is, what i have to do know to solve this problem. To prove that i buied the game, i could do a screenshot of my Steam profile with the Arma 2 cd key. Is this enough or did i need any other proof? Ihope you can help me. Regards Marbo13