[Samba] Problem integrating Samba with External LDAP

[Cool The Breezer]

Hello Group,
                 I am quite new to samba as well as linux(centos 5.3). I am 
trying to share some directories in my linux server so that users can access 
these folders like Windows share. For that I am trying to integrate samba with 
our ldap server so that anybody having ldap credential can access the shares. 
However I am facing the problem. Till now I am only working with 
 /etc/samba/smb.conf and using testparm to calidate smb.conf file. The content 
of smb.conf

[global]
        workgroup = MYGROUP
        server string = Samba Server Version %v
        password server =
        passdb backend = ldapsam:ldap://x.y.z.a
        username map = /etc/samba/smbusers
        log file = /var/log/samba/%m.log
        ldap admin dn = uid=_e3user,dc=AAA,dc=net
        ldap group suffix = ou=Groups
        ldap idmap suffix = ou=Idmap
        ldap machine suffix = ou=Computers
        ldap suffix = dc=AAA,dc=net
        ldap user suffix = ou=Users
        idmap backend = ldap:ldap://lx.y.z.a
        idmap uid = 10000-20000
        idmap gid = 10000-20000
        cups options = raw

[homes]
        comment = Home Directories
        valid users = AAA\%S
        read only = No
        browseable = No

[printers]
        comment = All Printers
        path = /var/spool/samba
        printable = Yes
        browseable = No

[output]
        comment = Doceng output folder
        path = /opt/doceng/output
        read only = No
        guest ok = Yes

[downloads]
        path = /home/_e3user/downloads
        read only = No
        guest ok = Yes


On restarting smb service, I am getting following error 
Failed to retrieve password from secrets.tdb
Let me tell you that _e3user is just another user in ldap system 
i.e. dap://lx.y.z.a and its not ldap admin. I would really appreciate your help.

- RB