The hideBuiltInItems() not working?

What’s the matter :

This is my document class:

    public function UploadDoc ()
    {
        myContextMenu = new ContextMenu();
        myContextMenu.hideBuiltInItems();
        init ();
    }

I can see the context menu in both IDE and HTML. The AS2-old-style works well in both IDE and HTML ~
What’s the matter ?