GalCiv3 v3.05. Do not have Crusades or Intrigue expansion.
This is my 4th game now and have not been able to build cultural improvements such as the cultural center even after researching it. Starbases are able to build their improvments, but not on planets with free tiles available.
Influence is the favorite part of the game for me... is this a bug?
EDIT: Please note, the cultural improvements are not showing up in improvement list; i.e. they are not greyed out, they aren't even showing up at all. Yes, they are fully researched and I have even researched beyond them.