Original Sins, Single player:
One of my planets was under attack by another faction.
So, I tried to set up defense and repair platforms and received the message: Another structure is in the way.
No other structure was in the way ( honest) and the planet was upgraded to the max.
Secondly the enemy had already knocked out several of my forward defenses.
I did have one trade satellite in orbit.
Quit pending a search for a solution.
Thanks for any help.