[Dovecot] trouble with deliver in 1.0.4

[Jack Bailey]

Ok, here's one for the idiot file.  I just installed dovecot-1.0.4 on my 
personal system for testing, a system which has to be the simplest 
dovecot configuration possible.  deliver is barking about something with 
which version 1.0.3 has no problem.  I looked over the wiki, googled, 
and see nothing wrong.

The error:

deliver(jjb): Sep 07 21:39:40 Fatal: Failed to create storage for 'jjb' 
with mail 
'mbox:/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/:INBOX=/var/mail/jjb'

In dovecot.conf:

  userdb passwd {
    # [blocking=yes] - By default the lookups are done in the main 
dovecot-auth
    # process. This setting causes the lookups to be done in auth worker
    # processes. Useful with remote NSS lookups that may block.
    # NOTE: Be sure to use this setting with nss_ldap or users might get
    # logged in as each others!
    #args =
    args = blocking=yes
  }

and

mail_location = mbox:~/:INBOX=/var/mail/%u

Clues generously accepted,
Jack