I've learned something about my problem (previously posted in the Crashes During Gameplay thread).

After the last updated, Steam says I'm missing one game cache file. So I did what was recommended by the Steam community and reinstalled the game. Still missing one game cache file. So then I completely uninstalled the game and reinstalled it again. STILL MISSING ONE GAME CACHE FILE.

Does anyone know where I can find this file on the disk so I can stop screwing around with it?