[Dovecot] Problems after upgrade (0.99.x -> 1.0.x)

[fazer69 at o2.pl]

Hello :)

I had a working Dovecot 0.99.x with the following dovecot.conf:
###
ssl_disable = yes
disable_plaintext_auth = no
login = imap
verbose_proctitle = yes
default_mail_env = maildir:%h/Maildir
auth = default
auth_mechanisms = plain
auth_userdb = passwd /etc/passwd
auth_passdb = shadow /etc/shadow
auth_user = root
protocols = imap pop3
###

Then I've downloaded, compiled and installed Doveot 1.0.rc6,
I tried lot of "possibilities" in the new dovecot.conf
but I always get :

dovecot: Dovecot v1.0.rc6 starting up
dovecot: Login process died too early - shutting down
dovecot: child 15288 (login) killed with signal 11
dovecot: child 15289 (login) killed with signal 11
dovecot: child 15290 (login) killed with signal 11

Some add. info:

# dovecot -n
# /usr/local/etc/dovecot.conf
ssl_disable: yes
login_dir: /usr/local/var/run/dovecot/login
login_executable: /usr/local/libexec/dovecot/imap-login
auth default:
  passdb:
    driver: shadow
    args: /etc/shadow
  userdb:
    driver: passwd


How can I get the new Dovecot acting as the old one?
I don't use pam (which seems to be default now),
simply shadow passwords (Slackware). 
http://wiki.dovecot.org/UpgradingDovecot did not help me.

TIA,
websafe