-i aiglx
which should say (==) AIGLX enabled (with a bunch of errors after that). If it doesn't get loaded, you can force it by adding :
Option "AIGLX" "true"
to Se... what the program is trying to do. I won't quote it here because I'm too lazy to reproduce it. However, it basically is saying that the gtk-window-decorator has caused a problem with the X server because it couldn't load the .xml file it pointed to during launch.
This is the case becau... piz-gnome it expected it.
=== The Solution: ===
It's dirty but it works. Simply download any metacity theme of your liking (from [[http://gnome-look.o