Comment 1 for bug 223555

OK, I've fixed this by moving .gconf/desktop/gnome/peripherals/keyboard up to my home directory. Everything now works just fine, and, of course, I still have all the configuration files if people need them to fix the bug. I can also help by testing things.

This is still a bug, of course. "Upgrading Ubuntu made my computer unusable" is not the user experience you want.