High CPU usage in menus

If you open a menu and click two ore more times (eg double click) on a menu item, that
is disabled, displays a submenu or is an seperator, the CPU usage of the program that
has created the menu goes to 97% - 100%. It takes very long to highlight an other item
an clicking one doesn't work anymore. The security dialog on CTRL+ALT+ENTF and the
task manager still works, but the rest of the GUI seems to hang.