It means you are probably still connected with a planet he colonized that is still on "your" side of the closed warp point. Maybe there is another explanation...
As for poplulation... The total number of population determines the bonuses. Both will multiply per the growth rate. If any of them is not a native breather of the planet's atmosphere, the planet will be domed. Growth of both populations will stop when the planet is at its max capacity, domed or not. Having alien races on the planet will negatively affect the planet's happiness (See FAQ for details).
Slick.
[ June 15, 2003, 18:24: Message edited by: Slick ]
Do they have a planet hidden inside a sensor-blocking storm?
Do they have any moons hiding behind the main planet?
Try looking in the "Planets" window, and choose "All planets"
If you can see any enemy planets in that list, you're probably in contact with them through that planet.
You were right.
I thought I had every planet settled in my 20 something systems but I had missed one and they had settled on it.
I had been so busy with everything else I hadn't noticed.
Situation has been rectified.
Thanks for letting me know about the racial mixture thing too!