Game Crashing/freezing

Hey guys,
I've got the demo version. I'm having a problem; when I try to select which type of head to use, the game freezes up and an error pops up saying "Step() failed!: [string "..."]:179: attempt to index field 'FireOrder' (a nil value)"
I've tried looking through some of the files to see if I could find 'FireOrder' and I have had no luck.
Any suggestions?
I've got the demo version. I'm having a problem; when I try to select which type of head to use, the game freezes up and an error pops up saying "Step() failed!: [string "..."]:179: attempt to index field 'FireOrder' (a nil value)"
I've tried looking through some of the files to see if I could find 'FireOrder' and I have had no luck.
Any suggestions?