Can't use any kind of "super" key combinations for keybindings in Ubuntu 12.04 from the control center
Install CompizConfig Settings Manager (CCSM)
sudo apt-get install compizconfig-settings-manager
Open CCSM from System Tools>Preferences>CompizConfig Settings Manager
Open "Commands" under the General group. Enable by check marking the box on the left.
Log off, log on. (Restart X)