font rendering broken in edgy

Do you use gtk2-engines-gtk-qt (and does ~/.gtkrc-2.0 exist)? Are you using _current_ Edgy (minus xserver-xorg-core)?

No, I am using the default ubuntu theme on an up to date edgy system.

ii xserver-xorg-core 1.1.1-0ubuntu1 X.Org X server -- core server
ii xserver-xorg 7.0.22ubuntu6 the X.Org X server
ii ubuntu-artwork 31 Ubuntu themes and artwork
ii human-gtk-theme 0.1-0ubuntu1 Edgy GDM themes (typo in the title ?)

it was working fine before the update of ubuntu-artwork and renaming of its dependancies.

Why are you saying "(minus xserver-xorg-core)" ? Is there a known problem with it ?

update: I have just launched a Qt app to check and it has the same problem, it is not a gtk/pango thing.
I might be related with the last xft update:
 xft (2.1.10-1ubuntu1) edgy; urgency=low
 .
   * Merged with Debian experimental
   * Fixed libfreetype6-dev Build-Depends

I have this version, I updated it without noticing at the same time as gtk engines.
I just tried reverting to version 2.1.8.2 (from dapper) but this did not solve my problem.
Any other idea ?

cut from nvidia site

Any distribution with Xorg 7.1

Please note that the released NVIDIA Linux graphics drivers do not currently support Xorg 7.1 (version 1.0 of the Xorg video driver ABI) and are not expected to work correctly.

If you use Xorg 7.1 with a current driver release, you may see rendering corruption (fonts may be rendered improperly or not at all, etc.) and possibly other problems. Recent NVIDIA X drivers will print a warning message of the form below if they detect an ABI version mismatch:

    (EE) ============= WARNING WARNING WARNING WARNING =============
    (EE) This server has a video driver ABI version of 1.0 but this
    (EE) driver is designed to work with versions before 1.0. The
    (EE) driver will continue to load, but may behave strangely.
    (EE) Please check http://www.nvidia.com/ for driver updates or
    (EE) downgrade to an X server with a supported driver ABI.
    (EE) ================================================== =========

Please check your Xorg log file (/var/log/Xorg.0.log) for this warning if you are not if the Xorg release you are using is affected. The 1.0-8762 NVIDIA Linux graphics driver release should basically work if you disable its RENDER acceleration with Option "RenderAccel" "0", but it is recommended that you use an older version of Xorg until support for Xorg 7.1 has been added to the NVIDIA X driver.

just add option "RenderAccel" "0" to xorg.conf to 'fix" the problem
and wait until nvidia solve this problem

Indeed, I was using the nvidia binary driver. I thought it would not work at all without explicitely telling it to ignore ABI changes...
Great to have xorg 7.1 then, and sorry for the noise!
I am marking the bug as rejected as they is nothing we can do with it, until a free drivers exists :/