вот что работает у меня:

RedHat Enterprise ES v3
samba 3.0.2-6.3E

--------- krb5.conf ----------
[logging]
    default = FILE:/var/log/krb5libs.log
    kdc = FILE:/var/log/krb5kdc.log
    admin_server = FILE:/var/log/kadmind.log

[libdefaults]
    default_realm = DOMAIN.LAN
    dns_lookup_realm = true
    dns_lookup_kdc = true
    ticket_lifetime = 24000

[realms]
    DOMAIN.LAN = {
    kdc = srv-pdc.domain.lan:88
    admin_server = srv-pdc.domain.lan:749
    default_domain = domain.lan
    }

[domain_realm]
    .domain.lan = DOMAIN.LAN
    domain.lan = DOMAIN.LAN

------------------------------

----------- smb.conf ---------
# Samba config file created using SWAT
# from 192.168.110.31 (192.168.110.31)
# Date: 2004/05/26 19:36:34

# Global parameters
[global]
    dos charset = CP866
    workgroup = DOMAIN
    realm = DOMAIN.LAN
    server string = File Server
    interfaces = 192.168.110.0/24
    bind interfaces only = Yes
    security = ADS
    allow trusted domains = No
    obey pam restrictions = Yes
    max log size = 1000
    socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
    os level = 0
    preferred master = No
    local master = No
    domain master = No
    dns proxy = No
    wins server = 192.168.110.1
    ldap ssl = no
    idmap uid = 10000-65000
    idmap gid = 10000-65000
    hosts allow = 192.168.110., 127.
    strict locking = No

[tmp]
    path = /tmp
    valid users = '@DOMAIN\Domain Admins'
    read only = No
------------------------------

и все работает как часы