ulfben,
I have installed proposed version of the plug-in. But the problem with categories still exists. BTW this bug occures only on the main page (see e.g. https://z86337.infobox.ru – main page, https://z86337.infobox.ru/test_wp/?page_id=125 – child page).
In addition, source code on the main page contains following rows:
<b>Warning</b>: substr_count() [function.substr-count]: Empty substring. in <b>/home/www2/users/z86337/htdocs/test_wp/wp-content/plugins/wp-dtree-30/wp-dtree_gen-functions.php</b> on line <b>173</b>
