samba - Jul 2003 - Samba Beta 3 + LDAP as PDC : Subnet mask problem

Hi,

We dispose several class C networks where all the windows pc should 
logon on one samba server acting as PDC. Due to our firewall we have to
set the subnet mask of the machines 255.255.255.0 or 255.255.255.128.
The problem is: 
   Our samba server is in the network:
                   192.168.1.0 netmask 255.255.255.0
   Our clients are in the network:
                   192.168.2.0 netmask 255.255.255.128
                   192.168.3.0 netmask 255.255.255.0
                   192.168.4.0 netmask 255.255.255.140

The clients in 192.168.3.0 could log on but the other clients could not log on.
They can even become member because when trying to add the machine, I get the
error message : domain does not exist. When I change the subnetmask to
255.255.255.0 it works but the internet doesn't work anymore because of
the firewall.

Any idea what that could be ???

Georges Goebel