Its joining a NIS/Samba based domain.
I have also set the passwd encryption in smb.conf as such,
encrypt passwords = yes
smb passwd file = /etc/samba/smbpasswd
Also, in lists.samba.org,
I read a few posts that said it could be due to the number of letters of the domainname being odd-numbered. Well, I have successfully added other machines to the domain before.
Thanks.