samba - Jun 2004 - Problem "The specified network name is no longer available"

Hello,

I have samba 2.2.7a-9.3.91mdk   installed on a mandrake 9.1 box . ( I 
have upgraded to a 3.0.2a-3mdk  version, but the problem remain the same)
When I installed it, one year ago , all is ok . Now, 90% of the time( 
but not all the time),  I cannot write on the shares from any w2k box.
(The problem arised when I upgraded with w2k SP4, but I am not sure)

When I copy a file to any share , there is a popup :
"Cannot copy xxxx: The specified network name is no longer available."
then the file appears on the share, but  with a size of zero.

same problem arises when deleting a file :
"Cannot delete xxx : Cannot find the specified file"
and the file is deleted.

the logs gives : (grosminet is a w2k sp4 box)

tail /var/log/samba/log.grosminet
[2004/06/20 21:31:32, 1] smbd/service.c:make_connection_snum(705)
 grosminet (192.168.0.10) connect to service archive initially as user 
fcorne (uid=501, gid=100) (pid 31596)
[2004/06/20 21:31:37, 1] smbd/service.c:make_connection_snum(705)
 grosminet (192.168.0.10) connect to service archive initially as user 
fcorne (uid=501, gid=100) (pid 31597)
 
nmblookup3 -S  grosminet
querying grosminet on 192.168.0.255
192.168.0.10 grosminet<00>
Looking up status of 192.168.0.10
        GROSMINET       <20> -         M <ACTIVE>
        GROSMINET       <00> -         M <ACTIVE>
        GROSMINET       <03> -         M <ACTIVE>
        ALIENS          <00> - <GROUP> M <ACTIVE>
        ALIENS          <1e> - <GROUP> M <ACTIVE>
        FCORNE          <03> -         M <ACTIVE>
        ALIENS          <1d> -         M <ACTIVE>
        ..__MSBROWSE__. <01> - <GROUP> M <ACTIVE>


I have searched the archives without sucess.

Any help will be very appreciated !

FC

Here is the configuration :
the internal network is 192.168.0.xxx
the samba server 192.168.0.5  is also a router  and works only for the 
internal network.
The firewall is completly open for the internal network.

samba-server-3.0.2a-3mdk

[global]
       workgroup = ALIENS
       server string = Samba Server %v
       interfaces = 192.168.0.5/24
       map to guest = Bad User
       log file = /var/log/samba/log.%m
       max log size = 50
       socket options = TCP_NODELAY SO_KEEPALIVE SO_RCVBUF=8192 
SO_SNDBUF=8192
       printcap name = cups
       os level = 255
       dns proxy = No
       printer admin = @adm
       hosts allow = 192.168.0., 127.
       printing = cups

[homes]
       comment = Home Directories
       read only = No
       veto files = /.*/
       browseable = No

[printers]
       comment = All Printers
       path = /var/spool/samba
       create mask = 0700
       guest ok = Yes
       printable = Yes
       print command = lpr-cups -P %p -o raw %s -r   # using client side 
printer drivers.
       lpq command = lpq -P %p
       lprm command = cancel %p-%j
       browseable = No

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

[pdf-generator]
       comment = PDF Generator (only valid users)
       path = /var/tmp
       printable = Yes
       print command = /usr/share/samba/scripts/print-pdf %s ~%u //%L/%u 
%m %I "%J" &

[archive]
       comment = Archive
       path = /archive
       read only = No
       guest ok = Yes

[share]
       comment = Shared Directory
       path = /home/share
       read only = No
       guest ok = Yes