I was never able to get Gnome to work on Zorin, Gnome is usually one of the easier desktops to get functioning.  I am going to re-install Zorin on the assumption that something probably went wrong.  It will be down for a couple of days.  We will also be going from the free Zorin Core to the paid Zorin Ultimate.  It is reasonably priced at about $21 US ($19 EU) and includes a Gnome 2 and Mac OS Desktop layout as well as 1.5GB of other software not included in core so I think it will be a good upgrade.