[Dovecot] Big problems after upgrade from beta8 (FC5) to rc21

[Jim Garrison]

After upgrading a working system from FC5's beta8 to rc21, one
vhost is failing with:
> dovecot: Feb 05 09:54:30 Error: POP3(user at mydomain.com):
> open(/var/mail/vhosts/mydomain.com/david/user, O_CREAT) failed: Not a
> directory
> dovecot: Feb 05 09:54:30 Error: POP3(user at mydomain.com):
> mkdir_parents(/var/mail/vhosts/mydomain.com/user/.imap/INBOX) failed:
> Not a directory
> dovecot: Feb 05 09:54:30 Error: POP3(user at mydomain.com): Couldn't open
> INBOX: Internal error occurred. Refer to server log for more
> information. [2007-02-05 09:54:30]
> dovecot: Feb 05 09:54:30 Info: POP3(user at mydomain.com): No INBOX for
> user top=0/0, retr=0/0, del=0/0, size=0
> dovecot: Feb 05 09:54:30 Info: pop3-login: Login:
> user=<user at mydomain.com>, method=PLAIN, rip=::ffff:4.242.120.235,
> lip=::ffff:216.75.55.45, TLS
Here's the entire dovecot.conf:

protocols = pop3s
ssl_cert_file = /etc/pki/dovecot/certs/popcert.pem
ssl_key_file = /etc/pki/dovecot/private/popkey.pem
ssl_ca_file = /etc/pki/tls/certs/ca-bundle.crt
ssl_parameters_regenerate = 48
disable_plaintext_auth = yes
log_path = /var/log/dovecot.log
mail_extra_groups = mail
mbox_read_locks = fcntl
mbox_write_locks = fcntl dotlock
protocol imap {
}
protocol pop3 {
}
auth_verbose = no
auth_debug = no
auth_debug_passwords = no
auth default {
  mechanisms = plain
  passdb passwd-file {
    args = /etc/dovecot/%d.passwd
  }
  passdb pam {
  }
  userdb passwd {
  }
  userdb static {
    args = uid=502 gid=502 home=/var/mail/vhosts/%d
mail=mbox:/var/mail/vhosts/%d/%n
  }
  user = root
}
plugin {
}

Did something changed between beta8 and rc21 in the index format and/or mbox
location?  If so, how do I recover so users can retrieve mail again?  Thx.