Samba works with W2003 but not with win-XP, with ZIM Application

I have a very strange problem happening, we have an ERP application that uses ZIM (SIENGE), and the users access it by a sharing in a samba server in a debian sarge linux 2.6.8.
The shortcut in the XP desktop: ( \\10.0.0.254\siengea\Util\zimrtmu.exe)
The SIENGE have some modules: Engineering, supplyes, commercial, financial, etc.
All of the PC clients are Win XP PRO 2002 SP2 with execption of only one that is W2003 server, and this is the only one that works perfectly for wathever user and with a good speed.

But for all the XP's, some problems happen:- some users connect and tunn de system, but very slow. We can take a coffe until the sistem show the repports.
- some users only can open the application after many tries. because gives a mesage thar the application is already in use by another user.

If I get a user with problem and acces with his login in the w2003 server, it works perfectly.
I already make some changes in the socket options and locks options in the smb.conf, but nothin resolved.

The version of samba are:
dpkg -l | grep -i samba
ii libcrypt-smbha 0.02-6         generate LM/NT hash of a password for samba
ii samba          3.0.14a-3sarge a LanManager-like file and printer server fo
ii samba-common   3.0.14a-3sarge Samba common files used by both the server a
ii smbldap-tools 0.8.7-4        Scripts to manage Unix and Samba accounts st
ii swat           3.0.14a-3sarge Samba Web Administration Tool

cat smb.conf
[global]
        unix charset = cp850
        workgroup = EMPRESA
        netbios name = SERVER
        username map = /etc/samba/smbusers
        admin users= @"Domain Admins"
        server string = Servidor PDC EMPRESA
        encrypt passwords = Yes
        obey pam restrictions = No
        guest account = nobody
        map to guest = Bad User
        log level = 0
        log file = /var/log/samba/samba.log.%m
        max log size = 50
        debug timestamp = yes
        domain logons = Yes
        preferred master = Yes
        domain master = Yes
        idmap uid = 1000-2000
        idmap gid = 1000-2000
        map acl inherit = Yes
        passdb backend = ldapsam:ldap://127.0.0.1
        ldap passwd sync = Yes
        ldap admin dn = cn=admin,dc=exemplo,dc=com,dc=br
        ldap suffix = dc=exemplo,dc=com,dc=br
        idmap backend = ldap:ldap://127.0.0.1
        ldap user suffix = ou=people
        ldap group suffix = ou=groups
        ldap machine suffix = ou=machines
        ldap delete dn = Yes
        map acl inherit = Yes

        #Acrescentado 09-11-2006
        os level = 254
        socket options = IPTOS_LOWDELAY TCP_NODELAY
        read raw = yes
        write raw = yes
        oplocks = yes
        max xmit = 65535
        dead time = 15
        getwd cache = yes
        lpq cache = 30

[PROFILES]
        path = /home/profiles
        read _only_ = No
        create mask = 0700
        directory mask = 0700
        guest ok = Yes

[homes]
        comment = Repositorio de %U
        create mask = 0644
        directory mask = 0775
        valid users = %S
        read _only_ = No
        browseable = No

# compartilhamento onde fica o aplicativo em ZIN
[SIENGEA]
        path = /home/siengea
        write list = administrator, @wheel, @staff
        read _only_ = No
        create mask = 0777
        directory mask = 0777
        guest ok = Yes
        delete readonly = Yes
        oplocks = no