downgrading xemacs using apt-get

[David Wright <ichbin@shadlen.org>]

The newest sid xemacs crashes at start. No problem, I think, that's the 
price of using unstable -- I'll just downgrade to testing. But it 
doesn't work!

> apt-get install xemacs21/testing

complains about unmet dependencies (isn't apt-get supposed to resolve 
depndencies?! it works with the sid xemacs.) If I resolve the 
dependencies "maunally" then

> apt-get install xemacs21/tsting xemacs21-mule/testing \
xemacs21-bin/testing xemacs21-support/testing

the install starts, but then it says:

Setting up xemacs21-mule (21.4.1-2) ...
emacs-install xemacs21
emacsen-common: Handling install of emacsen flavor xemacs21
emacsen-common: byte-compiling for xemacs21
/usr/lib/emacsen-common/packages/install/emacsen-common: xemacs21: 
command not found
emacs-install: /usr/lib/emacsen-common/packages/install/emacsen-common 
xemacs21 emacs19 failed at /usr/lib/emacsen-common/emacs-install line 
28, <TSORT> line 1.dpkg: error processing xemacs21-mule (--configure):
 subprocess post-installation script returned error exit status 29
dpkg: dependency problems prevent configuration of xemacs21:
 xemacs21 depends on xemacs21-mule (= 21.4.1-2) | 
xemacs21-mule-canna-wnn (= 21.4.1-2) | xemacs21-nomule (= 21.4.1-2); 
however:
  Package xemacs21-mule is not configured yet.
  Package xemacs21-mule-canna-wnn is not installed.
  Package xemacs21-nomule is not installed.
dpkg: error processing xemacs21 (--configure):
 dependency problems - leaving unconfigured

What's going on? How do I downgrade xemacs? Thanks...