[Samba] some clients cannot login

[Osmany]

I have a problem that's happening randomly in my network. Starting a
couple of weeks ago, some clients (All of my clients are running Windows
XP)on my network cannot login to their sessions and windows brings out
an error saying that the domain controller is not available or is
blocked. I don't understand why this is happening, seeing that other
clients can perfectly log in their computers in domain sessions. In the
same server I have a dns(bind9) with a dynamic zone that is
automatically updated by the dhcp. Does anyone have any experience on
this? Can anyone help me solve this? 

this is the output of testparm:

Processing section "[homes]"
Processing section "[netlogon]"
Processing section "[Profiles]"
Processing section "[printers]"
Processing section "[print$]"
Loaded services file OK.
Server role: ROLE_DOMAIN_PDC
Press enter to see a dump of your service definitions

[global]
	workgroup = OC.QUIMEFA.CU
	netbios name = PDC
	interfaces = 127.0.0.0/8, eth2
	bind interfaces only = Yes
	passdb backend = ldapsam:ldap://localhost
	passwd program = /usr/sbin/smbldap-passwd %u
	passwd chat = *New*password* %n\n *Retype*new*password* %n\n
*all*authentication*tokens*updated*
	syslog = 0
	log file = /var/log/samba/log.%m
	max log size = 1000
	server signing = auto
	socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
	printcap name = cups
	add user script = /usr/sbin/smbldap-useradd -m '%u'
	delete user script = /usr/sbin/smbldap-userdel %u
	add group script = /usr/sbin/smbldap-groupadd -p '%g'
	delete group script = /usr/sbin/smbldap-groupdel '%g'
	add user to group script = /usr/sbin/smbldap-groupmod -m '%u' '%g'
	delete user from group script = /usr/sbin/smbldap-groupmod -x '%u' '%g'
	set primary group script = /usr/sbin/smbldap-usermod -g '%g' '%u'
	add machine script = /usr/sbin/smbldap-useradd -w '%u'
	logon path = 
	logon home = 
	domain logons = Yes
	os level = 35
	preferred master = Yes
	domain master = Yes
	dns proxy = No
	wins support = Yes
	ldap admin dn = cn=admin,dc=oc,dc=quimefa,dc=cu
	ldap group suffix = ou=Groups
	ldap idmap suffix = ou=Idmap
	ldap machine suffix = ou=Computers
	ldap passwd sync = yes
	ldap suffix = dc=oc,dc=quimefa,dc=cu
	ldap ssl = no
	ldap user suffix = ou=Users
	panic action = /usr/share/samba/panic-action %d

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

[netlogon]
	comment = Network Logon Service
	path = /home/samba/netlogon
	admin users = root
	write list = "@Domain Admins"
	create mask = 0755
	guest ok = Yes
	browseable = No

[Profiles]
	comment = Roaming Profile Share
	path = /home/samba/profiles
	read only = No
	profile acls = Yes
	browseable = No

[printers]
	comment = All Printers
	path = /var/spool/samba
	admin users = root
	write list = root
	read only = No
	create mask = 0600
	guest ok = Yes
	printable = Yes
	use client driver = Yes
	browseable = No

[print$]
	comment = Printer Drivers Share
	path = /var/lib/samba/printers
	admin users = root
	write list = root
	create mask = 0664
	directory mask = 0775