I propose that the initial 'groups' values for the 2
predefined modules are set to "Anonymous"
for 'login_box' and "Registered" for 'application_menu'. If
someone (like me) unchecks 'Display modules to all
groups always:' in 'Admin->General' without first
adjusting the Groups value for these 2 groups, he
cannot login again and is forced to edit the database