Tim, Darrell,
One problem with gentdmconf is that arch does not have an /etc/X11/Xsession file. So when gentdeconf creates the Xsession file with an include for /etc/X11/Xsession, the login fails. What needs to be changed is a simple check to make sure the file exists before sourcing it. i.e.:
[[ -r /etc/X11/Xsession ]] && . /etc/X11/Xsession