The gksu issue is not related at all, since users-admin doesn't use it (else, that would mean it's running as root).
I suspect no user is shown in the list, or the current user isn't. Is it the case? Can you test that by creating a test user using 'adduser' in a console and check if it's enough?
The gksu issue is not related at all, since users-admin doesn't use it (else, that would mean it's running as root).
I suspect no user is shown in the list, or the current user isn't. Is it the case? Can you test that by creating a test user using 'adduser' in a console and check if it's enough?