Ugly fonts after changing font settings

[Nigel Ridley]

Oneiric.

This is terrible :-(
I tried changing fonts to make Google Earth's fonts nicer - which they are now, but no matter 
what I try in System Settings -> Application Appearance ->  and various entries I can't get my 
system fonts back to looking nice again. No matter which fonts I try, or if I change the settings 
for the anti-aliasing, all my system fonts in all apps look as if they have no anti-aliasing.

How can I get things back to normal? I've tried logging out and rebooting but no joy.

Nigel