I have recently upgraded from karmic to lucid (plain ubuntu using gnome).

Everything worked fine, but the characters now aren't anti-aliased any more, as you can appreciate from the screenshot:

This is what I tried to fix the situation, unluckily without succeeding:

1. Used the regular option pane from System->Preference->Appearance->Font (smoothing, hinting...)
2. Edited the .fonts.conf file
3. Disinstalling (and then re-installing) the mstcorefont package
4. Changing the default Sans font to a font of my liking (e.g. Tahoma) from the abovementioned Appearance options

My ubuntu installation is quite standard, with the typical add-ons one might wish for usability. I used the ubuntu start script to make a few tweaks.

Thank you in advance for your help! :)