Thread:Extension talk:Access Control Panel/Special:SpecialPages doesn't work after ACP Install

Installed the ACP extension, added following line to my LocalSettings.php

require_once("$IP/extensions/UMEduWiki/AccessControlPanel/AccessControlPanel.php");

it works, but I can't access Special:SpecialPages, it returns Server Error, which is 500, usually means a serious php failure. Any ideas?