this bug has happened to my brother too. I completely wiped arma 2, arma 2 oa off of his computer thinking it might be something wrong with client sided textures but after completely reinstalling everything and updating to the latest version, the problem persists. A fix to this would be greatly appreciated. Also I am running the same version on my computer with no problems.
I used to have this problem all the time. I verified the integrity of all the arma 2 games i had installed on steam and then connected to a 1.7.1.2 server and had no problems. Not sure if verifying the game caches fixed or the server version I was trying to join before was too old.
I'm also having this problem. I've been told it's because the client and the server are running 2 different versions but I have no idea how to fix it since there are updates to the client files all the time and servers are always behind with the updates. I think I fixed the problem. I verified the integrity of all the arma 2 game caches i have installed on steam and then connected to a 1.7.1.2 server with no problems. Not sure if verifying fixed the issue or the server version i connected to fixed it.