I am on newly purchased/installed Sapphire HD7850 and got the same error. If you turn off exclusive full screen you can get it to launch. Then it seems when you are messing with the settings, switch the basic settings level to custom and leave "exclusive full screen" unchecked. Also maybe try to do all of your settings tinkering in the launcher and not the game. This is obviously not ideal. Looking for more info on a fix if anyone has one.