A reference to ${prefix} in /etc/dbus-1/session.conf is not being expanded, causing the problem.
To work around until this is fixed, edit /etc/X11/Xsession.options and comment out the line saying "use-session-dbus". --Ken Bloom -- I usually have a GPG digital signature included as an attachment. See http://www.gnupg.org/ for info about these digital signatures.
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