[capnq]

I think I've encountered this same problem, but only when I've put the colony ship in a fleet with an armed escort. When I gave the fleet the Colonize order, I'd get an error message that the escort couldn't load any cargo, and the fleet wouldn't have any orders. I've gotten around this by manually loading the colonists and moving the fleet away from the planet before issuing the Colonize order. (This also has the slightly odd result that the orders list ends up with a Load Population order between Move To and Colonize, but since there's no population to load at the target yet, that order doesn't do anything.)