I ran into this problem:
I'm trying to join to domain OES2 DSFW workstation with FreeBSD 8.2 + Samba Version 3.6.3 and I get the error:

SPNEGO login failed: Logon failure
failed session setup with NT_STATUS_LOGON_FAILURE
     libnet_JoinCtx: struct libnet_JoinCtx
         out: struct libnet_JoinCtx
             account_name: NULL
             netbios_domain_name: NULL
             dns_domain_name: NULL
             forest_name: NULL
             dn: NULL
             domain_sid: NULL
                 domain_sid: (NULL SID)
             modified_config: 0x00 (0)
             error_string: 'failed to lookup DC info for domain' USLA22.RU 'over rpc: Logon failure'
             domain_is_ad: 0x00 (0)
             result: WERR_LOGON_FAILURE
Failed to join domain: failed to lookup DC info for domain 'USLA22.RU' over rpc: Logon failure
With the same configuration file Samba Version 3.5.8 join to domain fine without errors.

Please tell us the new Samba may need to make some specific settings in smb.conf to work with the domain OES2 DSFW.
Time synchronized.

# net rpc testjoin -Uadministrator
Enter administrator's password:
Join to 'USLA22' is OK

list smb.conf
        netbios name = ASGV9
        idmap uid = 15000-20000
        idmap gid = 15000-20000
        winbind separator = +
        winbind use default domain = yes
        private dir = /etc/samba/private
        kerberos method = dedicated keytab
        dedicated keytab file = /etc/krb5.keytab
        client use spnego = yes
        workgroup = USLA22
        security = ads
        realm = usla22.ru

xadcntrl validate
Tree Name: USLA_TREE22
Server Name: .CN=s22.OU=OESSystemObjects.dc=usla22.dc=ru.T=USLA_TREE22.
Binary Version: 20605.00
Root Most Entry Depth: 0
Product Version: eDirectory for Linux x86_64 v8.8 SP6 [DS]

Checking for nameserver BIND
number of zones: 2
debug level: 0
xfers running: 0
xfers deferred: 0
soa queries in progress: 0
query logging is OFF
recursive clients: 0/1000
tcp clients: 0/100
server is up and running
zone details are dumped at /var/opt/novell/log/named/named_zones.info
Checking for Name Service Cache Daemon:                              running
Checking for RPC Endpoint Mapper Service                             running
Checking for Kerberos KDC Service                                    running
Checking for Kerberos Password Change Server                         running
Checking for Domain Services Daemon                                  running
Checking for Samba NMB daemon                                        running
Checking for Samba  WINBIND daemon                                   running
Checking for Samba SMB daemon                                        running
Checking for service sshd                                            running
Checking for rsync daemon:                                           running
# kinit administrator
administrator@USLA22.RU's Password:

# klist -l
  Principal                 Cache name      Expires
administrator@USLA22.RU   /tmp/krb5cc_0   Jan 30 02:53:20