Noobetynoob

I recently purchased Arma 2 Reinforcements on disc only to find out a majority of the online servers require you to have all of the DLC and the original game, so i purchased Arma 2 and Operation Arrowhead off of steam but cant seem to have them be "combined". I have a combined operations shortcut on my desktop but when i open it I get the message 'failed to load file "pmc\addons\air_pmc.pbo" - decryption of headers failed.' I uninstalled and reinstalled the Reinforcements part f the game so it would be s aved in the same place as the ones i downloaded from steam but still get that message and not all of the single player campaigns are there. Only Harvest Red, Operation Arrowhead, and EW are there. At the main screen there are 4 images showing the expansions active, i dont know if there should be more or not? But if anyone else has had the same problem and knows how to fix it I would love to hear it.