Delete High.lua and do a verification of integrity of game cache. 
Worked for me when I had that.   
 All operating systems - Verify integrity of game cache     
 Load Steam 
From the Library section, right-click on the game and select Properties from the menu. 
Select the Local files tab and click the Verify integrity of game cache... button. 
Steam will verify the game's files - this process may take several minutes. 
Once the process is completed, the Check Window will automatically exit.