In your config file you must fill out this section to get access.
PHP Code:
// ****** USERS WITH QUERY RUNNING PERMISSIONS ******
// The users specified here will be allowed to run queries from the control panel.
// See the above entries for more information on the format.
// Please note that the ability to run queries is quite powerful. You may wish
// to remove all user IDs from this list for security reasons.
$config['SpecialUsers']['canrunqueries'] = '';
You will need to post the database error that you got from your email here or you can contact support at vbulletin.com and they should fix that register problem in no time.