KDE will not run as any user other then root.
 

On my recent install of Arch + X11 + KDE, KDE will not let me log in as an unprivileged user. When I log in as my user name with KDM, the screen goes black for a moment and then KDM reappears. As root, KDE runs normally. Any idea on how I could run as a regular user?

Maritime,

I'm not sure about the proper fix for this and I'll anxiously await an answer from someone who know what the heck they're doing. But, in the meantime, log into KDE as root, create a new user (adduser command) and create a password for that user's account and try logging into KDE
with the new account you created.

Do any other wm's work? Have you tried xfce/gnome/etc?

If they do, then it's obviously KDE specific. Maybe there's a problem with the KDE config for your user? Move ~/.kde* out of the way and see if that helps.

If not, then it's X related, is there anything of note in the log file? /var/log/Xorg.0.log on Slackware, should be something similar.

This can happen if the user you are trying to log in as does not have a home directory or the permissions are not right for that users home directory. You can check by creating a new user with proper /home dir and trying to log in as that user.

Thank you, to everyone who posted, for your assistance. It now works.