Admin rights?

My log-in was setup with Admin rights. But, in some circumstances I am asked for the Administrator and password...I thought Admin rights are universal if you setup your log-in as an Admin?
An example is: While installing VLC I am being asked for the Administrator password and when I type my password, along with the administrator username, the response is that I am not an admin?

Yes, but my log-in has admin rights...why will it not work? Is there a difference between mine and the Administrator log-in?