So, just in case anyone else is experiencing the problem that I had, I plugged my laptop into my HDTV and played Demigod and it was super cool. However, when I wanted to play again, after unplugging the HDTV, my laptop screen didn't support the resolution the HDTV was at, and the D3D device just fails to get created.

I fixed it by going into the My Documents\My Games\Gas Powered Games\Demigod folder and edited game.prefs. There was a line in it:

primary_adapter = '1920,1080,24',

I changed it to

primary_adapter = '1440,900,60',

which is a resolution and refresh rate that my laptop screen supports, and the game started right up.

If someone's listening, this really should get fixed so that it falls back to some safe mode resolution and tries again, but until then, it's something to check if your game was working, then all of a sudden doesn't.