This has been happening too much lately. Usually after a character gets froze on a loading screen. You have to shut down the game, and then when you try to restart the game, it lets you log in, but will not let you actually start the game. It seems to be specific computer related, so I am thinking there might be a temp file I can delete or a line on a text file that can be deleted or changed to let the game actually load?
Red, I've seen reports of this on multiple threads. Did this just recently start happening? Please create a support ticket with your Dxdiag/Msinfo so we can look into this further.