samba - Jan 2006 - Server shows Linux client IP addresses, not names

The smbstatus utility won't show the names of the Linux machines running in 
this workgroup, but it does show the names of the WinXP machines.  

It looks like this:

$ smbstatus -b

Samba version 3.0.10-1.4E.2
PID     Username      Group         Machine
-------------------------------------------------------------------
23158   steve         users         192.168.0.10 (192.168.0.10)
18040   nancy         users         venus        (192.168.0.3)
 3001   nancy         users         mars         (192.168.0.5)
 2894   steve         users         192.168.0.2  (192.168.0.2)


The browse.dat file correctly shows the names and IP address of all machines 
in the workgroup, so obviously the names of the Linux machines are 
obtainable.  

The server is running Samba v3.0.10 on a CentOS machine.  The Linux clients 
are running Samba 3.0.14a on Fedora Core 4 machines 

The Linux clients are running a minimal smb.conf, just enough (in theory) to 
provide a NetBIOS name for lookup by the server.  This is the entire config 
file: 

[global]
  workgroup = WORKGROUP
  server string = Software Development
  max log size = 0
  security = user

So what am I missing to get the smbstatus util to reflect the names of my 
Linux machines?  

Thanks

> So what am I missing to get the smbstatus util to reflect the names
> of my Linux machines?  
Well it doesn't seem to be a Samba issue at any rate - here only about
50% of the machines show a name, the other 50% are IP only...and
they're all running XP.

Cheers,
Adam.