That's probably not his problem. I am having the exact same problem. I am betting he is using Vista 64. I have onboard sound disabled and am using XFI Xtremegamer with the most recent drivers.
My specs so maybe someone will have another idea.
AMD 64 4800 x2
ATI X1900XT (7.2 Cats, the 7.3 bluescreen me)
4 Gigs Gskill timed at 2-3-2-5
250 gig Hitachi HD
XFI Xtremegamer
Most recent version of direct x 9C
2 16x LiteOn DVD drives
I bought my copy of ArmA through Sprocket and it's version 1.05 according to their website.
Here is a copy of ArmA config file
language="English";
adapter=-1;
3D_Performance=8721.000000;
Resolution_W=800;
Resolution_H=600;
Resolution_Bpp=32;
refresh=75;
FSAA=2;
HDRPrecision=8;
lastDeviceId="4098,29257,22941763";
localVRAM=534124544;
nonlocalVRAM=1878257664;
Copy of my Destructis ArmA Profile
version=1;
blood=1;
viewDistance=1200;
terrainGrid=10.000000;
volumeCD=7;
volumeFX=7;
volumeSpeech=7;
singleVoice=0;
playerVoice=0;
gamma=1.000000;
brightness=1.000000;
fovTop=0.750000;
fovLeft=1.000000;
uiTopLeftX=0.000000;
uiTopLeftY=0.000000;
uiBottomRightX=1.000000;
uiBottomRightY=1.000000;
sceneComplexity=300000.000000;
shadingQuality=10;
shadowQuality=2;
soundEnableEAX=1;
soundEnableHW=1;
anisoFilter=2;
TexQuality=1;
postFX=1;
useWBuffer=0;