I have the steam version of Arma and I checked out the steam forums for it, and one of the threads told me to install beta patch 1.17 (North American Atari version, be sure to check which version you have.) After installing the game it still didn't run and then I decided to check the arma folder under steam, and voila! There's a shortcut apptly titled "Launch Arma Beta Patch 1.17." I feel like a total moron but anyways dudes, check your arma folder for the seperate shortcut.. This is defintely the last game I ever buy from steam that is developed by BIS...
