adding sub menus in Qt designer is impossible

When creating a main window in Qt designer (4.6.2), it is impossible to add sub-menus to a menu item. There is an icon that apears on the right side of the menu item but clicking it does not do anything instead of creating a submenu on the right. In previous versions of the package (4.5.*) it was working correctly.

I am using Kubuntu 9.10 with ppa enabled to run KDE 4.4.1 .
The Qt package is in version : 4:4.6.2-0ubuntu1~karmic1~ppa2