Sarge system now refusing all login attempts

[Carl Fink <carlf@fink.to>]

I apt-get updated the system this morning.  I now find that I can't
do anything that requires login authentication.  I noticed it when a
sudo attempt just hung forever.  Checking discovered that I can't
sign on as either root or a user, at any prompt including VT's (which
would rule out an X problem).  Any such attempt just hangs
indefinitely.

Everything else works fine.  I can open new xterms in my current X
session, for instance.  Load is low.

I'm afraid to reboot, because I might be permanently locked out.

Any suggestions?  I'm downloading a current Knoppix CD right now to
use as a boot disk if I can't get it bootable again, but that would
be very annoying.

Thanks.
-- 
Carl Fink               carlf@dm.net
Manager, Dueling Modems Computer Forum
<http://dm.net>