I get an error prompt telling me the application was unable to start and to close the launcher. I can't even start the game now.

You must have a problem with patch 2.1 (the 0x0000005 error or whatever its called)

Check online the list of issues that can cause that error....I had it and solved it by renaming some Adobe Acrobat .dlls (acaptuser.dll) to .dll.bak