Amongst an ocean of spurious online advice about this, including badly made youtube help videos and people insisting a complete reinstall of Arma 2 was needed, Sugar_Aussie's advice worked just fine for me. (for clarity, yes I use steam, and once having followed his advice I then launched with PlaywithSIX) So I created this profile just to say thanks. Great when you find someone who knows what they're talking about, is also succinct, and saves you pulling any more of your hair out. Mad Props to the antipodean.