Failing to reopen mailbox after SSH tunnel closure

[Michael Williams <williams@xxxxxxxxxxxxxx>]

I connect to an IMAPS server over an SSH tunnel (the IMAPS server isn't
visible from the internet). If the tunnel connection drops I
unsurprisingly get a message in mutt informing me the the mailbox has
closed. If I then reestablish the tunnel I am normally able to reopen a
mailbox without closing the original instance of mutt (e.g. "c!" to open
my inbox). mutt reopens the IMAPS connection without prompting me for my
password.

However, I have recently installed mutt 1.5.13 (on an Intel Mac using
Fink), and this process no longer works. If the tunnel drops, I
reestablish the it manually and try to reopen a mailbox in mutt, e.g.,
c!, but all mutt does is display the message: 

  SSL connection using TLSv1/SSLv3 (AES256-SHA) 
  
for several minutes before closing the mailbox again. I have to quit
mutt, restart it, reauthorize with my password, and then I am able to
reconnect to the IMAPS server. I have a rather flaky SSH connection, so
this is a considerable inconvenience. Does anyone know of anything I
might have set up wrongly?

The relevant bits of my .muttrc are:

  set spoolfile=imaps://localhost:1993/INBOX 
  set folder=imaps://localhost:1993/

And of my .ssh/config:

  Host ssh-gateway
          Hostname ssh-gateway.example.com 
          LocalForward 1993 imaps:993

I open this tunnel using, e.g. ssh ssh-gateway -N.

Thanks,
-- Mike