Thanks for this thread, I was a bit hopeful and followed the Samba howto on a Debian Etch based distro, and ran into the same problem that Macaruchi hit
"tdb_update_sam: Failing to store a SAM_ACCOUNT for [tom] without a primary group RID
Failed to add entry for user tom.
Failed to modify password entry for user tom"
I assumed the problem arose because I was installing on etch, and was about to reinstall to a Sarge based installation. I am not sure if this helps.