samba - Aug 2012 - Problem in Samba(3.5.11) authentication via PAM

Hi,
    I am unable to configure the samba authenticaton through pam. It says
the following error.

[2012/08/22 12:27:54.087297,  0] auth/pampass.c:823(smb_pam_passcheck)
  smb_pam_passcheck: PAM: smb_pam_auth failed - Rejecting User velusamy !

  My smb.conf file as follows,

      [global]
         workgroup = ASSURANCE
         security = user
         obey pam restrictions = yes
         encrypt passwords = no
   Could you please anyone help me on this problem.

Thanks,
Velusamy.