I just have installed Slackware 12.1 using kdm, configured almost everything and now I'm using the default logging manager (kdm), everytime that I logout from any window manager dri becomes disabled and it happened too in slackware 12 and 12.1-pre, the only way that I have to avoid this problem is to comment out the "#TerminateServer=true" line in /etc/kde/kdm/kdmrc
my /etc/X11/xorg.conf
http://pastebin.ca/1007197
and the /var/log/Xorg.0.log
http://pastebin.ca/1007200