You deleted all the default usergroups. Please do not do this. This should be less of an issue with future releases of CB, but as is CB expects them to exist.
I've corrected your usergroup permissions removing Public access to backend and fixing Registered as well as its child groups to have frontend login.
You'll need to re-create your usergroups. Notice "Registered" has an ID of "21". This should be "2". Please run the below query on your database to correct usergroups then test if working.
Code:
INSERT INTO `jos_usergroups` (`id`, `parent_id`, `lft`, `rgt`, `title`) VALUES (2, 1, 6, 19, 'Registered'), (3, 2, 7, 14, 'Author'), (4, 3, 8, 11, 'Editor'), (5, 4, 9, 10, 'Publisher'), (6, 1, 2, 5, 'Manager'), (7, 6, 3, 4, 'Administrator');
DELETE FROM `jos_usergroups` WHERE `id` = 21;
UPDATE `jos_usergroups` SET `parent_id` = 2 WHERE `id` = 19;
UPDATE `jos_usergroups` SET `parent_id` = 2 WHERE `id` = 20;
UPDATE `jos_user_usergroup_map` SET `group_id` = 2 WHERE `group_id` = 21;
UPDATE `jos_viewlevels` SET `rules` = '[6,3,13,8]' WHERE `title` = 'Special';
UPDATE `jos_viewlevels` SET `rules` = '[6,2,8]' WHERE `title` = 'Registered';
UPDATE `jos_viewlevels` SET `rules` = '[1]' WHERE `title` = 'Public';
UPDATE `jos_viewlevels` SET `rules` = '[2,20,8]' WHERE `title` = 'Free';
UPDATE `jos_viewlevels` SET `rules` = '[19,8]' WHERE `title` = 'Paid';
Note if your prefix is not jos_ please adjust as needed. Please backup before running. It will move your "Paid" and "Free" usergroups for you as well. It will also move users from the new Registered (21) back to the default (2). It also will correct the view access levels. So should be a run and done situation.
For future reference do not PM me credentials unless I specifically ask for them. Install review is only done if I suspect a bug or it can't be debugged through posts.
krileon
