Trying to reinstall exim4

[Carl Johnson <carlj@peak.org>]

  I was trying out postfix but I was unable to get it working the way I
wanted, so I tried to purge postfix and reinstall exim4.  I used
aptitude to select postfix to purge and to install exim4, exim4-base,
exim4-config, and exim4-daemon-light.  It seems to accept the
selections, but when it actually tries to install it, it gives the error
message:

E: Could not perform immediate configuration on 'exim4'. Please see
man 5 apt.conf under APT::Immediate-Configure for details. (2)

  I dropped the statement 'APT::Immediate-Configure "off";' into a file
in /etc/apt/apt.conf.d, but it still won't install exim4.  Does anybody
have any idea what I am doing wrong, and what I can do to install exim?
I am running this on a squeeze system.

Thanks for any ideas.
-- 
Carl Johnson		carlj@peak.org