Hi
http://www.webupd8.org/2011/05/virtualbox-408-released-with-gnome.html
"The latest VirtualBox 4.0.8 finally comes with GNOME Shell support.
I've tested it in Ubuntu 11.04, using a Fedora 15 virtual machine and
Gnome Shell worked great. According to the changelog, it should work
with both Ubuntu 11.04 and Fedora 15"
Rahul