What did you do to cause this? Admin settings, changed Allow Registration dropdown to No, clicked Save
What page were you on? admin/settings
What PHP and MySQL versions do you run? PHP Version 5.3.10-1ubuntu3.2 MySQL Version 5.5.24-0ubuntu0.12.04.1
Describe the defect: Changing allow registration to No and clicking Save causes a red message box to be displayed saying "Allow Registration must be set".
A fix for this is waiting for Jack's approval on Github.