[Users] Connecting with vnc to a VM defined as spice

Hello, I have a Windows XP VM in 3.2 beta defined as spice. If I want to connect from a client that only has vnc (a Mac for example) how can I do from User Portal? Even if the VM is powered off then I power it on, on the right I see only spice as an option... Does the user need any special right? And if I select run once form user portal and select vnc then it tries to fire up spice protocol and if I click on "..." icon, only spice is present and selected... Any pre-requisite on engine/node/vm/client? Thanks, Gianluca