> Typing "C-h k x" to try to find out what "x" is bound to fails:

I've tried "emacs -Q" and "DISPLAY= emacs -Q", but neither helps.

This is with the current CVS trunk, in GNU Emacs 23.0.50.31 (i686-pc-linux-gnu, GTK+ Version 2.12.0)
of 2007-12-02 on trpaslik
Windowing system distributor `The X.Org Foundation', version 11.0.10300000
configured using `configure '--with-gtk' '--prefix' '/usr/local' '--with-xpm' '--with-jpeg' '--with-png' '--with-gif''