Wow, dungeon generators are popular lately.
It doesn't run for me, either. Same error as Minor, and I'm using 0.99.92.
It had some looping that I didn't understand at the beginning of the event sheet. Such as in the very first event:
+ System: Start of layout
-> System: Stop loop "filly"
-> Wand: Set X to Tile.width/2
-> Wand: Set Y to Tile.height/2
-> System: Start loop "fillx" and run 1 times
I'll have to look into the start and stop loop thingies there, as I've never really noticed those before.
I've recently been using groups in a very similar way that you did, for flow control in tick-based loops and such. It works really nicely.