samba - Sep 2003 - Master Browser Election - extremely puzzled

I've been through the FAQ's, archives, etc. No joy. I have a RedHat
Linux
setup with a recent version of SAMBA - for some reason a remote system keeps
'fighting' to be a master browser - this is across a WAN link. And the
local
SAMBA is set up with OS=255 and preferred master=yes. Every 15 minutes or so
the two duke it out and my server wins - but things are flakey during that
period. I've checked the registry on that XP box but it does not reflect the
settings that would make it a master - any clues to this would be
appreciated.