[Dovecot] dovecot and postfix virtual mailbox domains, system users

[Dave]

Hello,
    I'm trying to get dovecot and postfix virtual domains working on an fc6
system. My software versions are postfix 2.4.5 installed from rpm and
dovecot 1.0.3 also installed from rpm.
    I'm only running secure protocols, pop3s at the moment, imaps later on.
I've set up postfix for virtual mailbox domains as per it's howto on the
subject and confirmed that email sent gets delivered to the virtual area,
which in this case is /home/vmail/domain.com/username/, there's a maildir
under that area and incoming mail gets delivered by postfix to that area.
In the first case the user is a shell user who has a login, in all
other cases the users will be completely virtual, having no login account at 
all.
 When i atempt to get mail from the server
using this user, the one with the login, i am getting a can not map username
coming from dovecot.
Here's my config:

# 1.0.3: /etc/dovecot.conf
base_dir: /var/run/dovecot/
log_path: /var/log/dovecot
info_log_path: /var/log/dovecot.info
protocols: pop3s
ssl_ca_file: /etc/dovecot/ca-cert.pem
ssl_cert_file: /etc/dovecot/pop.cert
ssl_key_file: /etc/dovecot/pop.key
ssl_cipher_list: ALL:!LOW
disable_plaintext_auth: yes
login_dir: /var/run/dovecot/login
login_executable: /usr/libexec/dovecot/pop3-login
valid_chroot_dirs: /var/spool/vmail
mail_extra_groups: mail
mail_location: maildir:/home/vmail/%d/%u
maildir_copy_with_hardlinks: yes
mail_executable: /usr/libexec/dovecot/pop3
mail_plugin_dir: /usr/lib64/dovecot/pop3
auth default:
  mechanisms: plain login
  verbose: yes
  passdb:
    driver: passwd
  userdb:
    driver: passwd

and the specific maillog error is this:

Apr 11 23:48:17 s15298471 dovecot: pop3-login: Login: user=<user>, 
method=PLAIN, rip=66.139.186.37, lip=74.208.64.129, TLS
Apr 11 23:48:17 s15298471 dovecot: POP3(user): stat(/home/vmail//user/cur) 
failed: Permission denied
Apr 11 23:48:17 s15298471 dovecot: POP3(user): stat(/home/vmail//user/cur) 
failed: Permission denied
Apr 11 23:48:17 s15298471 dovecot: POP3(user): Couldn't open INBOX: Internal 
error occurred. Refer to server log for more information. [2008-04-11 
23:48:17]
Apr 11 23:48:17 s15298471 dovecot: POP3(user): Couldn't open INBOX top=0/0, 
retr=0/0, del=0/0, size=0


I'd appreciate any pointers. I think i am close, but am not seeing it.
Thanks.
Dave.