error installing emacs?

["Alan Su" <alsu@cs.ucsd.edu>]

i just did an update for my potato box, and the only error that didn't
correct itself with several Install passes was emacs.  here's the
error, as far as i can tell:

install/dpkg-dev: Byte-compiling for emacs20
cp: debian-changelog-mode.el: No such file or directory
emacs-install: /usr/lib/emacsen-common/packages/install/emacsen-common-install emacs20 failed at /usr/lib/emacsen-common/emacs-install line 28.
dpkg: error processing emacs20 (--configure):
 subprocess post-installation script returned error exit status 29

does anyone know what's going on?  any ideas on how to fix it?
thanks!

-alan