[Dovecot] shared/public mailbox doesn't exist

[Eric Shubert]

I have 3 servers running dovecot 1.0.10. 2 of them are configured with a
shared/public namespace, but I'm having trouble getting it to work on
the third, even with 2 working examples to go by. There's something I'm
missing, and I'm hoping that someone here can see/tell what it is.

I've created the maildir for sharing:
# cd /home/vpopmail/domains/mydomain.com
# maildirmake shared
# chown -R vpopmail:vchkpw shared

Then added the configuration to dovecot.conf:
# shared namespace
namespace shared {
    separator = .
    prefix = shared.
    location = maildir:/home/vpopmail/domains/mydomain.com/shared
}

Restarted dovecot:
# service dovecot restart

When I try to subscribe to the shared namespace though with Outlook, I 
get: "Failed to subscribe the folder. Server responded: 'Mailbox doesn't
exist: shared'." When I try to subscribe with Squirrelmail I get: 
"ERROR: Could not complete request.
Query: SUBSCRIBE "shared"
Reason Given: [TRYCREATE] Mailbox doesn't exist: shared"

I've tried various combinations of permissions to no avail.

Suggestions welcome. I'm at my wits end.

-- 
-Eric 'shubes'