Same problem, very annoying.

I found a fix (at least for me). You can try this:

1. Backup @mod and Chache folder of Arma II OA
2. Reinstall Ama II OA
3. Uninstall battleye by open the unistall BE (.exe)
4. Overwrite the BEClient.dll and BEServer.dll in the Steam\common\ArmaIIOA\BattlEye folder with this ( http://www.battleye.com/downloads/arma2/BEClient.dll ) & ( http://www.battleye.com/downloads/arma2/BEServer.dll )
5. Install the BE with the BESetup
6. Start arma II OA from Steam and then quit in the menu
7. Place the folders previously backupped in the armaIIOA folder where originally were
8. it's good if you verify the chache before starting the game

done.

Same problem, very annoying. Can't play. I will try to reinstall arma II OA right now.