I have the same exact problem it happened with one of the past 2-3 beta patches my clan server is running beta patch 95054 and I have this problem now. I didn't have it before 95054 I've tried higher beta patches nothing works even with a clean install of arma 2 CO. Dayz still works perfect but arma 2 missions like insurgency wont run I crash as soon as I start to load into the server from lobby. Oddly enough ace mod works still but vanilla arma 2 just wont go. I've tried to delete the soundd.dll or w/e it was but no luck.