You may have to start from scratch again, but try running Arma 2 and Arma 2 Operation Arrowhead by themselves. In A2 OA, you can click on Editor, load up Chernarus, and see if the map loads that way.
If that doesn't work, then you'll need to start over.
Since you have Arma 2 and Arma 2 OA already loaded. In your Steam Library, right click on the A2 and A2 OA > Properties > Local Files > Verify Integrity of File Cache. Once verification is done, run Arma 2 and Arma 2 OA so the initial files are loaded in. If you have all of the DLC, that will load in except for Army of the Czech Republic. That will need to be done manually.
After that, make sure you have DayZ and DayZ Epoch downloaded from DayZ Launcher and the files are verified there too. Then look up Beatnik Bandits and join in.
It's important to run Arma 2 and Arma 2 OA before you get to Beatniks. You need to run those games before you start.
Hope this helps.
