I seem to have a semi-workable system after I started using the Feisty Fawn update of Ubuntu before it was released.
Selecting a failsafe Gnome session, then logging in got me a workable display.
Selecting Compiz as my window manager (instead of Beryl) and then right-clicking on the Workspaces icon and increasing the number of workspaces from 1 to 4 got me back to where I used to be.
Only problem that I know of now is that both beagle and trackerd start up when I log in and they both consume massive amounts of CPU almost all the time. Will have to investigate which indexing system I should use, and why they’ve changed from one to the other.