Administration screens gone..

[Chanchao]

I don't know how I managed this but all my administration screens are
gone, save for a few non-admin-rights ones.

There's two possible ways this may have come about:

Installing Xubuntu-desktop, and xubunty-system-tools, then uninstalling
xubuntu-system-tools again as they mostly match the Ubuntu ones.  After
that all my admin screens were gone. 

Secondly, it may have happened while adding another user with admin
rights.. and ended up with nobody with sudo/admin rights!  I managed to
correct this by going into recovery mode and so a 'visudo' to update the
sudoers file and adding my username as (ALL) ALL (same as root).  

So after that I can sudo again, but my admin screens are still gone.

What can be my next step to fix this?

Cheers,
Chanchao