Message sent successfully, ERROR: not saved to mail/sent-mail

[Theodore Hope]

Just installed the latest stable Horde, IMP, PHP, Apache, UW-IMAP.

Things work perfectly _except_ that when I send a message I get
the following in the top message window:

  "Message sent successfully, ERROR: not saved to mail/sent-mail"


I can create Folders, move msgs from one folder to another, etc.
INBOX works fine (of course), but when I send a message it doesn't
get put in "sent-mail".  I _can_ move or copy msgs from INBOX to sent-mail.

The strange thing is that when I send a message (the first time),
the "sent-mail" folder _was_ created with the standard header
info message ("DON'T DELETE THIS MESSAGE -- FOLDER INTERNAL DATA")
but the message I sent (and subsequently sent ones) never get
added to that sent-mail folder.   Very strange!

In defaults.php3 I have the following set, as required:

   $default->user_use_folders = true;
   $default->folders = 'mail/';
   $default->sent_mail = 'sent-mail';


This is my setup:
 BSDI (BSD/OS) 4.1 (all patched)
 apache_1.3.14
 php-4.0.3pl1
 Latest UW-IMAP (unpacks as "imap-2000", idents as "IMAP4rev1 2000.283")
 horde-1.2.3
 imp-2.2.3
 horde's phplib configured to use postgresql-7.0.2

Could this be a bug in IMAP (or PHP's IMAP interface)?
Anyone seen this?

Many thanks in advance.
 -Ted.