After invading a planet for the first time, a colony ship was being built. I attempted to change it to building nothing but it wouldn't do it. So I decided to let it build a colony ship because I needed one anyway. Well after it was completed it still wouldn't let me change it to the not building anything option. I could build anyship I wanted but it would not let me select the option to not build anything. So I got rid of the space port. Well about 40 turns later a colony ship comes out of that system that doesn't have a space port. And now all systems that are building ships can't choose the build nothing option. This was very annoying and since I didn't have the resources to support a never ending ship building spree I quit the game. This bug deserves attention.