[Samba] what's on port 139

[Andrew Greenhill]

Having trouble with Samba.
The config file passes the test (testparm)
The Server seems to be upa and running fine (smbclient -L localhost)
But can't seem to connect to it from other computers (running 2000 or 98)
They were able to connect once though.
What should be listed on port 139 in services. We have :
netbios-ssn
Does this sound right?
Appreciate any help/suggestions!!
Regards, Andrew