New Matisse layout: How can I add another Tab to the TabbedPane

Hi

I'm testing the new Free Design layout(Matisse) with the last QBuild
200509081355 on the WinXP SP2.
I have a JDialog with the main JPanel in which I have a JTabbedPane.
I'm able to add one JPanel (as Tab1) to the TabbedPane but I'm not able
to add another JPanels (Tab2, Tab3...)
I tried many ways (by drag&drop from the Swing Palette, by the popup
menu on the TabbedPane and the menu item "Add From Palette" and so on)
but no one is working, the error message
"java.lang.NullPointerException" always appears.

Does anybody have any idea how to avoid this error message ?

Jarek