Problems changing folder to inbox with Courier 0.46

[Matt Larson <mlarson@xxxxxxxxxxxx>]

I'm trying to switch to a different IMAP server and having an annoying
problem and I'd appreciate any help.

I'm using mutt from CVS HEAD against a Courier IMAP server.  (This is
the full Courier mail server package, version 0.46).  I can start up
mutt and it opens my inbox just fine, and I can switch to other
folders using the '=' shortcut (e.g., 'c =incoming.mutt-users').  But
I can't switch back to my inbox using the '=' or '+' shortcut.  If I
try 'c =', I see this message:

  Mailbox does not exist, or must be subscribed to.

I don't see this behavior using an older Courier IMAP server (IMAP
only, not the full package) nor a recent Dovecot IMAP server nor an
older Cyrus IMAP server.

Here are relevant muttrc lines:

  set folder=imaps://matt@<hostname>/INBOX      # where are the mailboxes (+ 
and = are shortcuts)
  set spoolfile=imaps://matt@<hostname>/INBOX   # Maildir incoming file 
(~/Mail/incoming)
  set imap_home_namespace="INBOX"       # IMAP path to your folders

I get the same behavior regardless of whether imap_home_namespace is
set to "INBOX" or null.

One last note: interestingly, I can switch back to the inbox using the
'!' character, i.e., 'c !' does work.

I'd be grateful for any suggestions and apologize in advance if this
is an FAQ (I looked but couldn't find anything).

Thanks,

Matt