Before you upgrade to SME6.0final I would make a copy of your /etc/passwd, /etc/group, /etc/smbpasswd, /etc/secrets.tdb /home/netlogon/netlogon.bat files and /etc/samba directory. Put it in your /root directory, as this is restored from a backup. The login script is wiped out regardless of how you upgrade. Your passwd and group files could be wiped clean of machine names needed to login to the domain.