Thread:Extension talk:Lockdown/Lockdown not showing user groups

I have some strange behavior with lockdown (1.16-r70092) using MW 1.16.5. When I write 'require_once("$IP/extensions/Lockdown/Lockdown.php");' to my LocalSettings.php the Special:Preferences page won't show my user groups anymore (even though they are displayed in the groups List (Special:ListUsers&group=bureaucrat)). I would not mind that, but it also deletes my userrights-permission (i.e. no access to Special:UserRights), so I can't setup the Lockdown Extension properly. Is there any way to work around that?