This is indeed VERY strange. I got a different error to you:<img src="http://dl.dropbox.com/u/6660860/error.png">
As you can see my error points to object_player_arms, at event 0 on the AI event sheet. So maybe the issue lies somewhere in the event sheet itself and not with a specific object? There isn't even an "Event 0" .
Sorry i can't really help more than that, this one has me stumped, but maybe it will guide you in the right direction on where to look for the problem .
I decided to test it some more and disabled the AI event sheet, and got this error:<img src="http://dl.dropbox.com/u/6660860/error2.png">
So maybe its not the AI event sheet at all. I also tried toggling different events on and off in all sorts of different combinations and NOTHING seems fix it .
I'm sure it will turn out to be something simple though