Right click on your start menu button and launch the menu editor. See the
first photo. Select from the 'settings' menu 'show hidden items' or something like that. If your old menus are deleted with the menu editor you can bring them back by right clicking on the menu item and choos 'restore' or something similar (I'm not behind kde/linux at the moment). If you really want to remove them because you can't add a item with the same name as a hidden item. You'll have to remove them by hand in ~/.kde/share/applnks or the rh-applnks in the same dir.