[Samba] guest share on a " security = user" server

[Andreas Moroder]

Hello,

our samba server runs in  security = user mode.
Now I need a share people can connect to, even if they are not in the domain.

I tried this configuration

[open]
comment = Fuer Scripte die via Mcafee gestartet werden
guest only = yes
#security = share
path = /san/san-lacie/abteilungen/allgemein/mcafee
read only = no
writable = no
printable = no
Browseable = No

but it does not work. Windows pops up the the logon window or , when I try
to start a script from the console it tells me ( translated from german ) "
unkonwn user or worng passowrd "

smbclient asks for a pwd too, but accepts a empty one.

What is wrong in my configuration ?

Thanks
Andreas