samba - Nov 2005 - Could not login to my XP laptop outside the LAN

Hello,

After a successfull installation of a Samba 3.x.x. server as PDC, 
i join the Samba PDC with a XP SP2 laptop and i open a session 
for the first time. OK

After, i wanted to open a session with this laptop, 
while having disconnected the cable network, and 
i had the message:
"could not open a session, because the domain is not available."

Note i am a user with a local profile and (local) administrators rights.

What i have to do ? 
Server side or Client XP side ? 
Server side: SMB options ?
Client side: Key registry or any strategy ?

Before with WXP/W2KP and W2K Server, all clients could 
login outside the LAN (or outside the office).

What changed ?. 

Thank you.

JMV.