I installed Cinnamon two days ago in Ubuntu doing this:
sudo add-apt-repository ppa:merlwiz79/cinnamon-ppa
sudo apt-get update
sudo apt-get install cinnamon cinnamon-session cinnamon-settings
But when I try to start a new session in Ubuntu with Cinnamon, it starts Gnome Classic instead Cinnamon. I don't know why, but could it be possible because there's no cinnamon-session and cinnamon-settings in the repository? I have watched videos of the installation and there was no problem, but when the videos were recorded there were those packages.
I just tried to install Gnome Shell and it happens the same thing. I can run Unity 3D and 2D.
I'm using VirtualBox, but I don't think that could be the problem, right?
(I'm using Ubuntu 11.10 64 bits)