Can't play the game - it goes to the background!

[Overwhelming]

The game just arrived in my mail. I've installed it, followed by both patches, in the correct order.

I've started a new campaign and even before I get to control my character, the game goes to the background (as if I did Alt+Tab). I can't return to the game, although I still listen to the game's sounds.

I have to terminate the game (Ctrl+Alt+Del) and start again, to get the same problem all over again.

I have windows vista 64bit and I have ArmA2 and all expansions and they all work fine. What coiuld be the problem? How can we fix this?

Edit: it happened while playing with the editor as well.

[Clowns2]

While running a server game from your own computer and this happens, check your RPT file. (computer/username/appdata/local/arma2oa). It may give you some idea as to what the issue is. How is your video memory and what are the settings on your game. Start with low settings and work your way up.