I just upgraded to Ubuntu 16.04 from 14.04.
When I run System Settings, my CPU usage goes to 100%, and the Settings window always remains in focus. I tried to open System Monitor to kill System Settings, but the focus kept on changing back to Settings. When I click the close button, the current instance of Settings closes, but at the same time a new instance of the window pops up.
The only solution I found was to log out of the system.
apt-cache policy unity-control-center:
unity-control-center: Installed: 15.04.0+16.04.20160413-0ubuntu3 Candidate: 15.04.0+16.04.20160413-0ubuntu3 Version table: *** 15.04.0+16.04.20160413-0ubuntu3 500 500 http://jp.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages 100 /var/lib/dpkg/status 15.04.0+16.04.20160413-0ubuntu1 500 500 http://jp.archive.ubuntu.com/ubuntu xenial/main amd64 Packages