I ran into a similar bug of the samba with the latest ubuntu 14.04 official release.
My Win7 laptop cannot connect to the Samba server, but I run the "smbpasswd -a <USER>" and it works.
it seems the "smbpasswd -a <USER>" was not persistent when I reboot the server, I have to rerun the "smbpasswd command to add user.
I ran into a similar bug of the samba with the latest ubuntu 14.04 official release.
My Win7 laptop cannot connect to the Samba server, but I run the "smbpasswd -a <USER>" and it works.
it seems the "smbpasswd -a <USER>" was not persistent when I reboot the server, I have to rerun the "smbpasswd command to add user.