[Dovecot] ldap auth error

[pch0317]

Hi,
I have dovecot 2.0.beta6 and I'm newbie with dovecot.
I try authenticate user via LDAP (MS ActiveDirectory).
I have errors in log:
mail dovecot: auth: Error: LDAP: binding failed (dn 
cn=administrator,ou=users,dc=my,dc=domain): Invalid credentials, 
80090308: LdapErr: DSID-0C090334, comment: AcceptSecurityContext error, 
data 525, vece

This is my dovecot.conf file:
protocols = imap
disable_plaintext_auth = no
listen = *
ssl = no
auth_mechanisms = plain
base_dir = /var/run/dovecot/
mail_location = mbox:/home/vmail/%n/

passdb {
driver = ldap
args =/etc/dovecot/dovecot-ldap.conf
}

userdb {
driver = ldap
args = /etc/dovecot/dovecot-ldap.conf
}

And this is my dovecot-ldap.conf:
hosts = 192.168.0.19
dn = cn=administrator,ou=users,dc=my,dc=domain
dnpass = password
base = ou=myuser,dc=my,dc=domain
scope = subtree
ldap_version = 3
auth_bind = yes
auth_bind_userdn = ou=myuser,dc=my,dc=domain

user_attrs = homeDirectory=home,uidNumber=uid,gidNumber=gid
user_filter = (&(objectClass=posixAccount)(uid=%u))
pass_attrs = uid=user,userPassword=password
pass_filter = (&(objectClass=posixAccount)(uid=%u))


Should I have any file in /etc/pam.d ?

Thanks