Hi, probably you have broken User Manager as I wrote before, and all ACL is broken also. Maybe somebody hacked your website, and this is visual sign of it. Somebody tried to take control over users and broken this section. ! Gavick Team never modifying a Joomlal core files ! And you are first person since publishing this template few years ago with this problem, it should give you answer to your question.
I had failed to do the installation, and then I do the installation by making manual configuration.php and add users to my sql manually, anyway. Is this the cause? Since the beginning I did not feel the installation went smoothly. There is something less.