You didn't need to delete anything. You just broke all of your view access level and usergroup relationships.
You only need to insert the old usergroups again as they used completely different IDs then move your new custom groups under Registered.
Carefully review your users and ensure they all have valid usergroups. If you had custom view access levels then you need to review your entire site to ensure nothing is still trying to use them.
Code:
INSERT IGNORE INTO `jos_usergroups` (`id`, `parent_id`, `lft`, `rgt`, `title`) VALUES
(1, 0, 1, 22, 'Public'),
(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'),
(8, 1, 20, 21, 'Super Users');
If possible, restore back to before you deleted anything. Then just run the above query on your database. Next move your custom usergroups out of your custom Registered usergroup into the default Registered usergroup (has an ID of 2). It should then work fine and you'll have lost no progress or mappings.
krileon
