Frans Bouma (recently)
discovered that menuitems inside a flyout/popup menu are still accessible eventhough it's parent menu is already disabled. Although you won't be able to access the (sub)menu item(s), it's still available especially if you have a short-cut key assigned to it. DevExpress's barmanager also suffers the same behavior. Fortunately Jessica(jfo) of Winforms/WPF team posted a work around, although she indicate it won't be available in the highly anticipated service pack. Please do use the
workaround by jfo or make sure to check the enabled property before firing an action.