Update: I've tried disabling UAC, reinstalling DirectX and the latest drivers, disabling my firewall and antivirus, and even using the config files from when I played the demo but nothing's worked. I'm all out of ideas.
I've got a noob tournament coming up. 4v4, brand new players, 3 hours. I'd really like to participate in this but I can't if I can't even get the game to launch. :(
Help me, Obi-wan Kenobi... You're my only hope.