Self sign up stopped working

Self sign-up at our On-Demand instance (http://mariadb.org/jira) stopped working today. All sign-up attempts end up with "The email address provided is not from an allowed domain." Indeed, in the "Site administration" pane, self sign up is "Restricted by domain(s)", this option is switched on, with the empty domain list. Switching it to "No restrictions" does not work, [Save] button does not error out, but does not save either, if I reload the page it is still "Restricted by domain(s)".