[Samba] Problems with Access Control for Shares on Samba 2

[remote]

Hi all !

I have a question regarding the access control in Samba 2. I want to make shares available to the Windows Network for which only the owner of the share has write access. Other users however should be able to read and browse these shares. 
My smb.conf : 

global]
   workgroup = leat
   guest account = nobody
   keep alive = 30
   os level = 2
   kernel oplocks = false
   security = user

[hobbit5]
    comment = hobbit5 
    path = /ALPHA-DATA/hobbit5
    browseable = yes
    read only = no 
    guest = ok
    valid user = hobbit5 
;    force user = hobbit5

As far as I understand Samba, with this configuration any Samba user should be able to browse and read the hobbit5 - share, while only hobbit5 himself can write and delete within this share. 
However, what happens is that any Samba user can see the share in the Network Neighborhood, but except for hobbit5, none can enter it. Windows tells me that either the path is not correct or I don´t have the network privileges to do this. 

What do I do wrong ?

Thanks,

Jörg