Here follows a summary after several hours of struggle. :-)
After upgrading to qt-4.5 the problem happens between kde4 and qt4
applications where it looks like the fonts are shredded. To see an example of
what I mean see my desktop
http://www.fep.up.pt/docentes/jamatos/desktop1.png
with this nice artifacts. :-)
Funnily enough I don't get this problem with non-qt4 applications on kde and
if I change to gnome all the applications work as expected (including qt4
based apps).
I have moved away .kde and .kderc but the problem remains. I have tried the
same with $HOME/.config/Trolltech... and no joy as well. After entering the
first time the same problem with fonts would appear immediately.
I tried to use my wife's account that was empty and the problems does not show
there so I suspect that there is some configuration file somewhere that leads
to garbled fonts.
Since I was running out of time and without further ideas I have downgraded to
qt-4.4.3 where all works as usual.
Regards,
--
José Abílio