apt-get totally broken: "/var/cache/debconf/config.dat is locked"

[Andrew Schulman <andrex@alumni.utexas.net>]

This morning I made the mistake of remotely killing an 'apt-get update' 
that had not finished running on another terminal.  Now, apt-get is 
totally broken.  Whenever I try to install anything, I get:

debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by 
another process

and everything fails.  Right now I have 11 uninstallable packages.

I have hunted down and killed every running process that matches apt*, 
dpkg*, or debconf*.  Still the accursed lock remains.  I can't find any 
obvious lock files in /var/lock or /var/cache/debconf.

Judging by other traffic on this list this AM, I think my original 
hanging install was caused by the foomatic or openoffice.org updates.  
But I've now removed them, and the problem remains.

Can anyone help me to remove this damnable lock?
Thanks,
Andrew.