Jaws, I think I found out your issue. At least I ran into this and this was the fix.
After you open NILE an place an object, click on the arrow button. Its the one on the far left, second from the top tool bar. You building should show up.
It has to do with selection. The arrow button is the select / de-select tool. So if the select button isn't selected then the program doesn't know to show the objects. At least that is way I have found.