As of the last update I don't seem to be able to add starships from the Ships window into the PC ships window.
I do seem to be able to create a new ship, I just can't drag and drop an existing ship to the window. I already had a PC ship in that window, but I was unable to assign PC's as crew other than as passengers, and when I deleted the ship from the PC ships window, I now cannot re-add it.
Is there some special trick to adding a PC ship?