Instead of the message log page, I just get:

Section Error!

More information about this error
Stack trace:

• line 5744 of lib/weblib.php: call to debugging()
• line 3926 of lib/adminlib.php: call to print_error()
• line 9 of admin/report/messagelog/index.php: call to admin_externalpage_setup()

The more information url is: http://docs.moodle.org/en/error/admin/sectionerror

This looks to be the same issue as has been noted on the M&P discussion