Problem starting ArmA2: Operation Arrowhead+Combined operations

[Problem starting ArmA2: Operation Arrowhead+Combined operations]

A rookie mistake, agreed, I just had to close steam completely and run as an admin, everything works now. Thank you all for your help, for pointing that possibility out Placebo, and your time.

[Problem starting ArmA2: Operation Arrowhead+Combined operations]

Let me start by saying, forgive me if this is posted in a wrong forum, I couldn't find anything that seemed to fit the problem better.

I bought ArmA2: Combined operations on Steam, but I can't start Operation Arrowhead. It's the "No entry 'bin\config.bin/CfgInGameUI/MPTable.shadow'.

Error compiling pixel shader PSSpecularAlpha:0" problem, but when I try to solve it with the means posted on this forum, I find that the "ArmA2OA.cfg" doesn't contain a "class ModLauncherList" section. Here's what it does contain:

language="English";

adapter=-1;

3D_Performance=48387;

Resolution_Bpp=32;

Windowed=0;

I'm pretty bummed out, because I bought it to play the DayZ mod, but I can't get that to work either. Can someone tell me what to do?