Thanks for the replies! -- Upgrading works OK for me now. I've got the latest version and the latest patch. The only thing I can think is: when the upgrade kept crashing the game, my frigate was all the way at the "top" of the map (actually, about 3 tiles from the top) -- maybe that caused problems because the airship has to be rendered "above" the tile...
I have to say again how much I love this mod. Firaxis could learn a lot from it.
I love that the tech tree has more "vertical" choices, but doesn't tediously stretch out horizontally. It gives you real and tough choices, and eliminates the tedious redundancies you see in most 4x tech trees (Combat III -- Combat IV -- Combat V -- yech).
I love, love the Erebus random maps. It would take too long to explain why. And it's not just because I'm airshipping my Kuriotates over those mountains and shocking the heck out of my enemies.
As much fun as I had with 2 of the other FFH civs, I may never play any other civilization than the Kuriotates. The city restriction suddenly turns Civ into a much more interesting game than it has ever been for me.
Thanks again for a great game!