Yes, it's the lack of the correct shipset (not empire file) that causes the problem. The empire file defines the shipset to use and can't be changed, so you and your fellow players will need that shipset on their computer. (in Pictures/Races folder) Those that don't have it will get a random shipset from those they do have. Just download it at any time to fix the problem.
I played my entire KOTH game against Parabolize seeing a new shipset each turn. I am sooooo lazy!
