Yeah. Cookie is pretty spot on. It seems like the main issue is the Epoch Mod, the rest of the files seems fine.
But to go into more detail where to find everything, this is how you do it.
Step 1: Make sure files are validated for Arma 2. Go into Steam, right click on Arma 2, go to Properties, go to Local Files, click on Verify Integrity of Game Cache. Then wait for files to validate.
Step 2: Do the same thing in Step 1, but for Arma 2 Operation Arrowhead.
Step 3: Run Arma 2 Operation Arrowhead so the files are loaded properly.
Step 4: (I hope you're using DayZ Launcher cause this is how this Step works) Open DayZ Launcher, go to the Mods tab, verify DayZ mod.
Step 5: In the Mods tab, verify DayZ Epoch mod.
Step 6: Log into the server and try out that combo lock.