I have just rebooted from the upgrade of my Kubuntu desktop 8.10 64bits (with kde 4.2) to 9.04 beta, and every character of any kde application is totally scrambled, ugly and unreadable - as you can see in the attachment. KDM's fonts are ok, GTK fonts are ok too, and system consoles are ok (konsole is of course unreadable).
Plasma's widgets are unreadable too, except the time in the Analog Clock (very very huge font), but the date (smaller size) is unreadable.
This computer was up to date before the upgrade, using the last nvidia driver provided by jockey-kde (maybe -177), desktop effects on a dual screen and French localization. The upgrade did run smooth without error. It only prompted for a replacement of apport config file, which i acknowledged.
VGA compatible controller: nVidia Corporation GeForce 8400 GS (rev a1)
I have tried to change the kde fonts (& size) in System Settings > Appearance but it didn't changed the scrambling effect. Unexpectedly, the fonts were ok in the preview window of System Settings > Fonts.
I of course had the system rebooted one time after the upgrade, and i tried two times to reboot X without any changes.
I have just tried a 'sudo dpkg-reconfigure fontconfig' in TTY1 and since the fonts of freshly started KDE apps are good now. I then restarted X again and everything seems fine!
I wonder if this bug is really a duplicate of the gnome subpixel rendering bug : disabling the antialiasing effect in system settings > appearance > fonts did not solve the problem.