out-of-date summary in nnimap group

[David Carlton]

I read mail from an IMAP server.  When reading the mail from home,
I use nnml to grab the messages from the IMAP server; at work, I
use nnimap to brows the messages that I've received since the last
time I logged in from home.

After a recent upgrade of the work machine (the one where I use nnimap),
my Summary buffer is getting screwed up - it's showing me Subject:
headers that are out of date.  For example, say that one day I'm
at work, and messages 1 and 2 are:

  [ ###: foo ]  Old Message 1
  [ ###: bar ]  Old Message 2

Then I go home, grab those messages (using nnml), and I get three new
messages overnight.  ("New Message 1", "New Message 2", "New Message 3",
say.)  The next day at work, when I use nnimap to look at my mail, it will
show me:

  [ ###: foo ] Old Message 1
  [ ###: bar ] Old Message 2
  [ ###: baz ] New Message 3

instead of

  [ ###: goo ] New Message 1
  [ ###: gar ] New Message 2
  [ ###: baz ] New Message 3

(If I actually select one of the first two messages, it will show me
the correct contents - it's just the summary that's incorrect.)
Any idea what's causing this?  If I delete enough stuff (I can't remember
what all I deleted - all the relevant stuff in News/, and probably
my .newsrc), I can get the it to display the correct subjects, but obviously
that's a pain.

I'm currently using Gnus v5.10.6, in XEmacs 21.4p15.  I can't remember
what the old versions of Gnus/XEmacs were.

David Carlton
carlton@bactrian.org