Installed, played till crash, now unable to launch game

I installed the game, played for about 30 minutes and thoroughly enjoyed the expansion/beta.  I alt-tabbed while it was maximized, then tried to alt-tab back into game, I couldn't get video back (still could heard the audio from the game).  I ctrl-alt-del and force quit the game.  Even after a computer restart, the game doesn't get past the first 'Loading' screen, it crashes about 5 seconds after launching it.