Problems with multiple portals ( dynamically added )

Hi

I'm having some issues with portals.
Basicly each portal represents a week ( with seven days as columns ) and the portlets are tasks ( see tasks.jpg )

I have two portals added in codebehind and each of these has some portlets.
( In this case it's two portals because there are tasks in these two weeks - it could be more og less )

Moving the portlets from one portal to another is not a problem, but if I move all portlets to one of the portals ( leaving the other empty ), it seems that the empty portal gives me a problem. An error message tells me that the portal can't be found. ???

How do I fix that ... ???