@McGuin, try restarting your computer and then verifying the integrity of the game cache.

1. Restart your computer and launch Steam
2. From the Library section, right-click on the game and select Properties from the menu.
3. Select the Local files tab and click the Verify integrity of game cache... button.
4. Steam will verify the game's files - this process may take several minutes.

Next try the possible solutions listed on this page.

Lastly try switching to the profiling game branch. Instructions are linked. After downloading new data verify the integrity of the game cache.

If there are still issues after trying all of the above then prepare and upload a troubleshooting report.

For issues regarding Arma 3 you can file a troubleshooting report, also via an action available in the option menu in the upper right corner (gear icon)

If the report will not upload to the feedback tracker then try uploading to a free file sharing service such as Dropbox.