[Samba] Xp-pc's disappear in Network Neighborhood

[Bjørn Fahnøe]

I have this problem. Window Xp machines show up in Network neighborhood 
when they are started but after some time (20 minutes or more) they 
disappear.
I can find them with search computer.
Mapped network drives still work.
They reappear if I restart the pc
They reappear if I restart Samba

Its only a small home network so I do not log in to a domain.

Whats going on?????

My samba.conf
# Global parameters
[global]
	log file = /var/log/samba/log.%m
	ldap ssl = no
	socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
	printer name = Epson
	domain master = Yes
	map to guest = Bad User
	printer admin = @adm
	wins support = true
	dns proxy = No
	netbios name = BF-SERVER
	server string = Samba Server %v
	workgroup = BFHJEMME
	os level = 35
	unix charset = ISO8859-1
	max log size = 50
	 [homes]
	comment = Home Directories
	read only = No
	browseable = No

[printers]
	comment = All Printers
	path = /var/spool/samba
	create mask = 0700
	guest ok = Yes
	printable = Yes
	use client driver = Yes
	browseable = No

[print$]
	path = /var/lib/samba/printers
	write list = @adm, root
	inherit permissions = Yes
	guest ok = Yes


  [Alle]
	path = /var/Alle
	read only = No
	create mask = 0777
	directory mask = 0777