dselect problem with potato

["Gregory T. Norris" <haphazard@socket.net>]

For some reason dselect wants to remove an awful lot of packages from
my potato system: at, cron, debconf, exim, mailx, apparently all of
gnome, and a bunch of others.  When I run apt-get it seems perfectly
happy with everything that's installed, and nothing seems to be flagged
for removal in dselect... until I press <Enter> and get sent to the
conflict resolution screen.  I've been looking through the downloaded
Packages file, trying to trace all the way through the various
dependencies, but I can't seem to find any unsatisfied conditions which
could be the cause.

As an example, this is dselect's complaint about at:

     at depends on mail-transport-agent or mailx

In my case mail-transport-agent is provided by exim, and mailx is
installed as well, so that requirement would be satisfied if dselect
wasn't determined to remove them both.  Manually verifying the direct
and indirect dependencies for exim (run "pkg-revdeps exim" for the full
tree) doesn't turn up any unsatisfied conditions, however.

Here's what /etc/apt/sources.list looks like (edited for readability):

     deb http://http.us.debian.org/debian potato main contrib non-free
     deb http://nonus.debian.org/debian-non-US potato
         non-US/main non-US/contrib non-US/non-free

Any suggestions about what to look at next?  The system in question was
upgraded to potato roughly three months ago, and it gets updated on a
(more or less) nightly basis.

Thanx!