After 12.10 update (Jan 15/2013) my desktop has changed in ways I cannot explain. There is only the wallpaper, but the screen resolution is 600x400. No unity, no menu bar. I can bring up a terminal, in 600x400 res'n. I can ctrl-alt-del to logout. After logout, I get a menu bar with the only option to shutdown or login, again in 600x400 res'n. The previous version (3.5.0-21) operates perfectly.
What to do?