All purchased on Steam(ArmA 2, ArmA2 OA, Arma 2 BAF)
Windows Vista 64
Intel Core 2 Duo E8500
Ati (now amd ;) ) 4850 Running Catalyst 10-5 drivers
4 GB Ram
Same problem as everyone else here, I believe. Can't join OA or BAF servers, but can join original ArmA 2 servers.
Like someone else has mentioned, I was able to join a OA/BAF server right away after patch. Once I had left that server though, closed the game, did something else for a while, came back to OA/BAF, I was no longer able to join any server(except those with Battleye not required).
My Steam is set up to run as Administrator.