imap server not reopened after timeout

[Dan Christensen]

I've just recently started using nnimap to access a dovecot imap server.
I have

  (nnimap "jdc.math.uwo.ca")

in my gnus secondary select methods.  After not accessing the server for
a while, if I try to enter a group, I get an error, with the following
in the *Messages* buffer:

Retrieving newsgroup: nnimap+jdc.math.uwo.ca:INBOX...
Opening nnimap server on jdc.math.uwo.ca...
Denied server nnimap+jdc.math.uwo.ca
Opening nnimap server on jdc.math.uwo.ca...failed
gnus-select-newsgroup: Couldn't open server

Also, hitting `g' in the *Group* buffer does not update these groups.
If I do `ESC g' on one of the groups, the server is opened correctly.
Also, in the server buffer, `O' works.

And if I manually close the connection, Gnus does reopen it
automatically.  The problem only happens when the connection is
closed by the server.  I connect with starttls.

I believe Gnus is supposed to reopen the server automatically when
necessary.  Is this a bug, or is something wrong with my set-up?
Am I accessing the groups as foreign groups by accident?

Thanks,

Dan