Debugging an imap connection in gnus

[Paul Bibbings]

I've been reading my gmail in gnus for some while now, and without
issue.  I'm running gnus v0.11, emacs 23.1.1 (i386-mingw-nt6.0.6002) on
Windows Vista.  To connect to my gmail I've been using imap with an ssl
connection that uses a version of openssl bundled with the Cygwin
environment.  Today there was a major upgrade of Cygwin to 1.7.2-1
coupled with a release upgrade of openssl to 0.9.8m-1.  After the
upgrades, I can no longer connect to the imap server from gnus.

Clearly this is an issue that I will need to take to the Cygwin mailing
lists, but before I can I need to get some information out of my
Emacs/Gnus package about just what is failing, but I am failing myself
to get even that.

With an unchanged .emacs (the details of which I can provide, if
necessary) I'm merely getting the following message in the minibuffer:

   Mail source (imap :server imap.gmail.com :port 993 :user
   paul.bibbings@gmail.com :password ******** :authentication (quote
   login) :stream ssl :fetchflag \Seen) error (IMAP error: nil).
   Continue? (yes or no) 

This is very Gnus/Emacs-specific and not enough to take to Cygwin, but I
can't get any more than this.

These are the things that I have tried so far:

1. With (setq imap-debug t) I do indeed get some debug output, but it
   doesn't add anything other than what Gnus and Emacs are doing
2. With (setq imap-log t) I get nothing, despite the fact that the docs
   suggest that this should only be enabled when necessary because the
   logging output is verbose.

What I need is some output from the openssl connection itself, and
perhaps the weird thing here is that I can, in fact, get a successful
connection and login from a bash prompt to gmail's server using the
commands that gnus is trying to issue.  For instance, in the *Messages*
buffer I get:

   imap: Connecting to imap.gmail.com...
   imap: Opening SSL connection with `openssl s_client -quiet -ssl3
   -connect %s:%p'...
   imap: Connecting to imap.gmail.com...failed

where the equivalent at the bash prompt gets me:

   23:29:20 Paul Bibbings@JIJOU
   /cygdrive/d/emacs-23.1/bin $openssl s_client -quiet -ssl3 -connect
   imap.gmail.com:993
   depth=1 /C=US/O=Google Inc/CN=Google Internet Authority
   verify error:num=20:unable to get local issuer certificate
   verify return:0
   * OK Gimap ready for requests from 86.15.147.8 10if799592bkw.36

So, I'm not even sure that this /is/ an issue with Cygwin directly.

Perhaps as a starting point someone could help me to understand, in the
first error message from the minibuffer (given above), what the 

   (IMAP error: nil)

is actually saying.  What does Gnus actually see as failing?

Any help will be greatly appreciated.

Regards

Paul Bibbings