Can't build orbital refineries

For some reason my construction ships won't build orbital refineries.  I've researched them, built it on the map, but the construction ship won't go to it.  If I try and send it to the refinery manually it says 'target must be an unfinished structure'.  Yet I also know from looking at the graphs when I quit the game that a couple of AI have refineries that are producing resources.

This is my first game with the beta, and I've never had this problem before.