Manage Enrol Plugins - Error - Blank

I have upgraded to Moodle 2.5.2 (Build: 20130909).

Now, when I click on Plugins > Enrollments > Manage enrol plugins I get a blank screen with nothing to do.

Using debugging... this is what I got:

Fatal error: Call to a member function get_settings_url() on a non-object in /moodle/htdocs/lib/adminlib.php on line 5254

Please let me know what I can do to fix this error.