Comment 15 for bug 510059

This is what we used at one time to fix this problem.
Easy enough to try.

gksudo gedit /etc/samba/smb.conf

Find this section in the file:
####### Authentication #######
# “security = user” is always a good idea. This will require a Unix account
# in this server for every user accessing the server. See
# /usr/share/doc/samba-doc/htmldocs/Samba-HOWTO-Collection/ServerType.html
# in the samba-doc package for details.
#security = user

Uncomment the security line, and add another line to make it look like this:
security = user
username map = /etc/samba/smbusers
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