On Mon, 30 Mar 2015 09:44:27 Craig Sanders said,

i was kind of hoping that someone would know something really obvious and stupid about X / lightdm / x sessions / xfce / whatever that i didn't. no such luck.

Do not know if this will help but............ The Xserver requires a child process under control of the user in order to stay up, this process is usually the window manager. If this process exits for any reason the Xserver shuts down. Try another window manager with something like, In the file ~/.Xsession a line like "/usr/bin/fvwm2", Note no ampersand, this is required. Note the Xserver config may have the exicuting of this line disabled. This is enabled in /etc/X11/xinit/xinitrc with the line "$HOME/.Xsession". I run fvwm window manager this way no problems. Lindsay