I appreciate the patience. After doing this, the role is still unassigned. If I click the "eligible only" button, the governorship disappears, even though I have leaders of AC2-8 and the position is AC3. Possibly some kind of DB error? I've already reinstalled once.
I haven't weighed in because what you describe is the correct procedure. So either there's a bug, or you're doing something wrong that all of us automatically do correctly without even realizing we're doing it.
I would do some experimenting. First, copy your database (Stevefire.mdb) to another directory - that way you can make changes without worrying about trashing your game. (When you're done, simply copy it back into the Aurora directory.)
Can you assign other officers using the procedure you use? For example assigning a colonel to command a ground unit, or a naval officer to command a ship.
Is it just Earth? Hit the "create colony" button on another world, e.g. Mars (select world in F9 screen, and hit button). You should see the governorship of that world show up as a level-0 post. Try assigning one of your civilian administrators to the world using the same procedure. No matter whether or not it works, you'll either have an "aha" moment when you realize what you're doing wrong, or you won't
If not, you should probably post the issue as a bug in the bugs thread. Make sure to save a copy of the DB in case Steve wants it.
John