I tried doing what you said, which means that the one and only change I made to the xml was changing flames_expire_chance to 0. and that was enough to fix the CTDs. so it seems like Vista has a problem with flames expiring, probably from no-yield tiles like ice and desert. I'm not sure about deserts, but somebody mentioned them and they do have in common with ice that they are no-yield tiles. I'm sure about the ice, cuz deleting flames on ice in the worldbuilder DID solve the CTD. for one turn only, though. then they reappear alongside with the dreaded CTD. that's really strange. Damn you, Vista! nobody likes you!