[libvirt-users] connecting to virtualbox with libvirt

I am trying to connect to the virtualbox hypervisor through libvirt. If I am doing it correctly, virsh -c vbox:///session should get me connected. I am on F14 64 bit. I tried this with both vbox 3.2 and 4.02. I keep getting the following error: error: no connection driver available for vbox:///session. What am I missing? Thanks, Gary