[Samba] samba loses its browse list

[Csere Matyas]

hello

i've asked this question a while ago, but noone could help me with it.. 
ill try to give more detail in this message:

so, there is a samba file server on our lan, and the clients are all 
windows XP's.
when i start the samba server, it becomes the local/domain master, and 
starts to build up its browse list (i can see that from the browse.dat 
file, and when i browse the network i can see computers in it)
but after some while, cant quite define the time, it loses the list 
(browsing then network doesnt show up computers, and the browse.dat file 
becomes EMPTY)

anyone has a clue, what could be causing this?
or, do you need any other information?

thanks in advance,
cserem