For your changes to be effective, you must have NS1.MEDIATEMPLE.NET and NS2.MEDIATEMPLE.NET designated as your nameservers with your registrar. See (mt) Media Temple's DNS/Nameserver information for more (mt) Media Temple nameserver details.
It is also possible to edit your zone file here, in anticipation of an upcoming change, to using (mt) Media Temple's nameservers even if you don't currently use them for your domain.