metacity-setup doesn't work after upgrading metacity from 2.3.987-r2 to 2.4.0. it does not crash, but i couldn't change metacity-theme or font settings, and next gnome-sessions always sets 'default' metacity theme. remerging metacity-setup with latest metacity doesn't help. for a while i'm back to 2.3.987 (maybe newest metacity-setup would fix this, i'll try to find cvs version).
This is an upstream issue where metacity-setup looks for the themes in the /usr/share/metacity/themes folder, but metacity 2.4.0 has changed the location , and the theme format, so now they reside in /usr/share/themes/$Name/metacity-1/ This is documented in my FAQ page for Gnome at http://gentoo.org/~spider/ along with a short script to list all avaiable themes. you can still change themes using gconf-editor or gconftool-2 , see the Metacity README for more information.