Yes of course we also use Samba but we are in trouble with "seven" clients that cannot join the domain so I'm searching for alternate solutions ...
If your having a problem with samba, perhaps emailing samba@lists.samba.org will help. Also, on a quick "off chance" have you applied the registry entries needed to windows 7 to join a samba 3.x domain? this same issue stumped me for many hours some weeks back.
Take a look at this link
http://technet.microsoft.com/en-us/library/ee681622(WS.10).aspx
That fixed my issue, for Windows server 2k8/r2 also.
William