Hi Gorgo,
I once had a similar problem in a non-gold game where the computer players had only space ports on their planets. This suggested to me that somehow the AI didn't get selected as 'normal' and as a result were 'nothing'. I just started a new game and the problem went away (I'm guessing there was a hic-up when the game went to find my AI opponents).
Perhaps start a test game, research propulsion, and scout out your neighbours to see if it improves. You could also load all of the AI manually and go into their settings to ensure that they are set to 'normal'.
Hope that helps a bit. If not, ask in this thread again, and somebody will help ya
