It's just the beta, beta 1 and 2 are just what they are calling the major patches. If you have access to the advent right now you are up - to - date. If not then verify the integrity and check to make sure updates are automatic.

Just verify the integrity of the game cache, that prevents you from having to uninstall and reinstall.

 Go to the game in your library and right click on it, then go to properties. This will open a new window. Go to the "Local Files" tab at the top of this window and then click on "Verify Integrity of Game Cache". After that it should apply the newest update and start up just fine.