The error message in the title is what i still get after i had steam check my game files five times.
Each time a small file is downloaded but that obviously doesn't fix my problem.
I have a retail ArmA II and have bought the Arrowhead expansion on Steam.
My system is a Phenom II x6 T1100 on a Asus Crosshair IV Mainboard, 16 GB Corsair 1333 DDR3 Ram, the graphics card is a ATI HD6950 with 2GB VDDR5,
I have a 120 GB SSD system disk and 3 1TB samsung HD's in a RAID5, The OS is Win7/64 Ult. and my AV is Bitdefender.
Needless to say that ArmA II OA is the only Software which troubles me on this system, even Cliffs of Dover is running well.
Help please.
SOLVED!
I did a complete uninstall of ArmAII and OA and reinstalled OD per Steam -> it works now.