samba - Dec 2005 - Samba DMB "loses" machines in the Network Neighborhood

I have a long running problem with my configuration of Samba as a domain
master browser. After nmbd comes up, all the machines on the network are
viewable in the Network Neighborhood as they should be. But about half an
hour later, Samba seems to lose track of several machines; they no longer
appear in NN or /var/cache/samba/browse.dat.

I recently upgraded to a packaged version 3.0.20b (for Slackware) trying to
fix the issue with previous 3.0.x version that was installed, but to no
avail.

The [global] block of my smb.conf:

[global]
        workgroup = 203

        security = share

        printing = CUPS
        printcap name = CUPS
        load printers = yes

        wins support = yes
        local master = yes
        domain master = yes
        preferred master = yes
        OS level = 255

        smb ports = 139 445
        interfaces = eth1 eth2
        bind interfaces only = yes
        hosts allow = 10.11.20. 127. 192.168.0.

> But about half an hour later, Samba seems to lose track of several
> machines; they no longer appear in NN or /var/cache/samba/browse.dat.
Do you have any other NMB servers on your network?  I have two Windows
2000 servers, and they somehow manage to 'overwrite' Samba's browse
list shortly after startup.

When I first installed Samba I put some text into the 'server comment'
field, but I removed it almost a month ago - yet it would seem
that because at any given moment at least one of the Win2k machines has
been available, this outdated data is still being cached and the wrong
server comment is still showing up.  I think it will take a power
outage or some other method of switching off all Windows PCs and
servers at the same time in order to 'flush' this outdated data away.

Cheers,
Adam.