After an abortive attempt to use the new ATI/AMD Catalyst driver for my notebook (my card seems too exotic) I needed to return to the onboard Intel graphics. Removing the fglrx Catalyst drivers was easy, but getting unity to play after was not. I ended up reinstalling with the following two commands. Perhaps a little over the top, but all is now well.
sudo apt-get autoremove --purge unity unity-common unity-services unity-lens-* unity-scope-* unity-webapps-* gnome-control-center-unity hud libunity-core-6* libunity-misc4 libunity-webapps* appmenu-gtk appmenu-gtk3 appmenu-qt* overlay-scrollbar* activity-log-manager-control-center firefox-globalmenu thunderbird-globalmenu libufe-xidgetter0 xul-ext-unity xul-ext-webaccounts webaccounts-extension-common xul-ext-websites-integration
sudo apt-get install unity unity-common unity-services unity-lens-* unity-scope-* unity-webapps-* gnome-control-center-unity hud libunity-core-6* libunity-misc4 libunity-webapps* appmenu-gtk appmenu-gtk3 appmenu-qt* overlay-scrollbar* activity-log-manager-control-center firefox-globalmenu thunderbird-globalmenu libufe-xidgetter0 xul-ext-unity xul-ext-webaccounts webaccounts-extension-common xul-ext-websites-integration