haliparotin
SME server is a NT style domain controller. You cannot join an Active Directory server to a Windows NT style domain controller and expect Active Directory services to work, as the Active Directory services are not supported.
Please search these forums as I'm sure the topic has been raised quite a few times.
Also please read
http://wiki.contribs.org/Advanced_Sambaparticlualrly this paragrapgh right at the end.
"Active Directory
NONE of the currently supported server roles will fully integrate with an Active Directory network environment. The currently supported server roles will work with NT4 network or windows workgroup environments only. Specifically, those who desire to deploy the Domain Member server role need to be aware that this server role WILL NOT provide domain membership in a Active Directory domain, only a NT4 domain."