[Samba] Samba4 on Ubuntu 12.04 won't join existing domain

[pccom frank]

root at u1204:/etc# /usr/local/samba/bin/samba-tool domain join delltest.pccom.ca  DC -Uadministrator --realm=delltest.pccom.caFinding a writeable DC for domain 'delltest.pccom.ca'Found DC dell2008.delltest.pccom.caPassword for [WORKGROUP\administrator]:Failed to bind - LDAP client internal error: NT_STATUS_INVALID_PARAMETERFailed to connect to 'ldap://dell2008.delltest.pccom.ca' with backend 'ldap': (null)ERROR(ldb): uncaught exception - None  File "/usr/local/samba/lib/python2.7/site-packages/samba/netcmd/__init__.py", line 175, in _run    return self.run(*args, **kwargs)  File "/usr/local/samba/lib/python2.7/site-packages/samba/netcmd/domain.py", line 552, in run    machinepass=machinepass, use_ntvfs=use_ntvfs, dns_backend=dns_backend)  File "/usr/local/samba/lib/python2.7/site-packages/samba/join.py", line 1082, in join_DC    machinepass, use_ntvfs, dns_backend, promote_existing)  File "/usr/local/samba/lib/python2.7/site-packages/samba/join.py", line 78, in __init__    credentials=ctx.creds, lp=ctx.lp)  File "/usr/local/samba/lib/python2.7/site-packages/samba/samdb.py", line 56, in __init__    options=options)  File "/usr/local/samba/lib/python2.7/site-packages/samba/__init__.py", line 114, in __init__    self.connect(url, flags, options)  File "/usr/local/samba/lib/python2.7/site-packages/samba/samdb.py", line 71, in connect    options=options)root at u1204:/etc# uname -aLinux u1204 3.2.0-33-generic #52-Ubuntu SMP Thu Oct 18 16:29:15 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
/usr/local/samba/sbin/samba --versionVersion 4.1.0pre1-GIT-d6983f4
It has no problem to create a new domain and allow XP to join it.
Your help will be appreciated.