When I upgraded Ubuntu from 14.04 (Trusty Tahr) to 14.10 (Utopic Unicorn), the computer booted up fine after the restart. But after logging in, the Window Manager didn’t start up!
TL;DR … To fix this, delete the
~/.config/dconf/user file (or rename it), and then restart the computer.
When I logged in, the desktop was there with all the icons on it, but the top menu bar, and the side-bar were missing. When I opened up a window by clicking on a folder icon in the desktop, it would open, but it would be missing the title bar. So, basically seemed like the Window Manager was missing. After deleting the above mentioned file and restarting, it was all good again!