hi kayaker,
i was having some sort of the same problem, and all i had to do was to make sure the posts were in the correct location in the building MOS. that is, they should belong to the wall and floor where they were placed.
go to building MOS in d-cam 6-4, highlite the floor/wall where the post should belong, click on "add" for elements, select the posts, right click when done, and at the prompt click ok. if you go back to ground they should show now.
hope this helps