I finally solved the problem. My /etc/environment had a single line LANG=nl_NL@euro which (for unknown reasons) caused the problems. Removing this line did the trick.
Now that I can login as root again, I still wonder why this is causing trouble in the first place and also why it only prevents root from logging in (and only in multi-user mode) and others still can login. Anyway, thanks to all who replied and (indirectly) helped me to solve the problem. -- Xaveer Leijtens <[EMAIL PROTECTED]> -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]