I tried Mint 12 on real hardware and cinnamon worked fine.
I just installed Virtualbox on Win 7 x64 and then 64bit Mint 12 on a VM, and updated it first, then I installed cinnamon with synaptic package manager, then I logged out and enabled cinnamon. But it doesn't work. I still get the built in WM when I log back in even tho cinnamon is enabled in the login window settings.
Just a sec. Let me reboot the VM to make sure what's up.... Reboot... No. It shows in the login screen as the enabled option, but when I log in, it looks just like it did when I first installed Mint. So cinnamon is not working.
Something strange about VM that keeps Cinnamon from working?