Fix for getting kicked off the game.

Step 1: Close steam, and launch it again as Adminstrator.

Step 2: Right click on Arma 2 in your steam library, then click on Properties, after that click on the Local Files tab, the click Verify integrity of game cache. Then wait for that to finish

Step 3: Repeat Step 2 but instead of Arma 2 Verify the Arma 2: Operation Arrowhead.

Edit: Step 4: After you have gotten that done, launch Arma 2, close it, then launch AO, then close it.

Step 5: Now launch Sixlauncher or whatever you use, and you should be able to connect!

Is this the error you get when exiting the map? Error 140 or something?