samba - Oct 2009 - Password prompt in security = share

Hi,

    I need to create a samba server with multiple shares.

    Imagine the scenario:

Server
\_Public
\_Depto1
\_Depto2

    When a windows user try to access Server for the first time, he can access
\\server and list all of shares.

    When click in Public, can access without password prompt, full access.

    When click in Depto1, samba ask for password, but in the password dialog,
Username is blocked (Guest) and password is blank.

    In a Windows 2008 server, the username and password are in blank too, but
when try to log using a user declared in 'valid users', logon failed.

    Using: security = user, It works! But, ask for password to access the
Server.

Some idea to help me?

Best Regards.

Rafael Camacho