[Samba] DNS error when join domain (Win 7 -> SAMBA 4)

[petro at iei.org.br]

I stood up a samba 4 (4.0.10) Active Directory domain controller on
a Debian Wheezy server, configured in accordance with the SambaAD DC
HOWTO <https://wiki.samba.org/index.php/Samba_AD_DC_HOWTO> . I'm trying
to join a Windows 7 Enterprise Edition client to the domain. Windows
responds with: 

Error while attempting to join the domain
"MYDOMAIN":
Fails when trying to resolve the DNS name of a domain
controller in the domain being accessed .. 

The DNS (Samba Internal DNS
Server) is working right. I tested with the commands: 

host -t SRV
_ldap._tcp.samdom.example.com.
host -t SRV
_kerberos._udp.samdom.example.com.

host -t A
samba.samdom.example.com.

Yesterday I got success to add a computer to
the domain, but today it did not work. I made no change from yesterday
to today.

Could anyone help me? 

Thanks.

Rafael.