- are you trying to run any mods?
- did you use game shortcut or tried to launch ArmA directly?
The process went as follows:
1: installed game through GoG installer
2: Started Arma 2 from the desktop shortcut
3: Installed "Play withSIX" for DayZ
4: Launched Play withSIX
5: Downloaded DayZ through Play withSIX
6: Started DayZ through Play withSIX (this was the first time the OA .exe was started, and the startup failed)
7: Tried starting OA through its original .exe in its installation directory
GOG's Arma 2 is very fragile I've come to realize. Make sure you have a completely fresh install (remove all registry entries and folders again.) Then run the shortcut in the start menu as admin. It should work fine right then and there. Then apply the multiplayer serial code. (I've noticed this is where the trouble starts happening.)
For mods, proceed one at a time; install CBA then launch the game, install JSRS then launch the game, etc.
Installing and configuring very carefully with GOG's version is how I got it working.
Thanks for the tips. I'll try to follow that routine