Simple_Slip

Few days ago i had buy ArmA II:Combined Operations in Steam Store. But in singleplayer misson "Razor-2" i've found a strange bug. Player needs to check three points. When i check two of them and coming to third my game is freezing. I tried to reinstall whole Arma II + Arma II:AO, Drivers, DirectX. Tried to install it on another PC. I even had buy non-steam cd-key, but it's still freezing at the same point. I asked about this bug on many forums and another users told me to ask about it here. Hope you can help me. My PC: cpu i5 3.2 Ghz, 4Gb RAM, nvidia gtx 560 1024Mb, hdd 1,5 Tb, OS win 7 x64