After hours of trial and error I found a solution using the menu function. I use this command to show the page title of the root of the page, regardless of the level of the page itself. Works like a charm. See
http://www.emilynijhuis.nl/cms (look at the category title above each left menu).
<?php show_menu2(0, SM2_ROOT, SM2_MAX, SM2_CRUMB|SM2_CURRTREE,'<h2>[menu_title]</h2>','','','',false,false); ?>