[Samba] Samba Win2k problem

[asim_is at comcast.net]

I have a samba server version 2.2.7a-8.9.0 running on RedHat 9.0.  It is acting as a domain controller.  I have some win2k clients logging in to this domain and mapping home shares, shared drives, etc.  The network the servers are on is 1000Mb and the client networks are all 100Mb.  The client networks are linked via 1000Mb uplink.   The problem I'm having is that when a user copies a fair number of files (197 files equalling 34 MB in this case) from a mapped share J: to another directory on that same share, about 3/4 of the way through the copy, the share shows disconnected (a red x on the share mapping, and net use shows 'Disconnected    J:'.  Seems as though it's related to this:

[2003/12/22 11:10:55, 1] smbd/service.c:close_cnum(677)
  asim0369 (192.168.1.64) closed connection to service SYS
[2003/12/22 11:10:55, 2] smbd/service.c:make_connection(331)
  Invalid username/password for sys [smbguest]
[2003/12/22 11:10:55, 2] smbd/service.c:make_connection(331)
  Invalid username/password for sys [smbguest]
[2003/12/22 11:10:55, 2] smbd/service.c:make_connection(331)
  Invalid username/password for sys [smbguest]
[2003/12/22 11:10:55, 2] smbd/service.c:make_connection(331)
  Invalid username/password for sys [smbguest]
[2003/12/22 11:10:55, 1] smbd/service.c:make_connection(636)
  asim0369 (192.168.1.64) connect to service SYS as user tomd (uid=10001, gid=10011) (pid 26701)

Once these entries appear in the log, the share shows up as disconnected. I can still work in the share, add/modify/delete and so on, but the red X remains usually until I manually disconnect/reconnect(and sometimes that doesn't work).  

Also, why is win2k apparently connecting as nobody/smbguest(not sending user/pass?) first, and then later connect as the logged in user? 
 
Any help on this would be greatly appreciated.  Thanks in advance,

Tom Dangler

Here's my smb.conf:
[global]
   workgroup = WORKGROUPNAME
   netbios name = SAMBASERVER
   server string = FILE SERVER
   log level=2
   domain admin group = @administrators @domainadmins 
   printcap name = cups 
   load printers = yes
   printing = cups
  guest account = smbguest
   log file = /var/log/samba/%m.log
   max log size = 0
   security = user
  password level = 8
  username level = 8
   encrypt passwords = yes
   smb passwd file = /etc/samba/smbpasswd
   unix password sync = Yes
   passwd program = /usr/bin/passwd %u
   passwd chat = *New*password* %n\n *Retype*new*password* %n\n *passwd:*all*authentication*tokens*updated*successfully*
   pam password change = yes
  obey pam restrictions = yes
   socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
   os level = 99
   preferred master = yes
   domain logons = yes
logon drive = G: 
logon home = \\SAMBASERVER\%U
show add printer wizard = yes
logon script = %U.bat
add user script = /usr/sbin/useradd -d /dev/null -g 100 -s /bin/false -M %u 
#============================ Share Definitions ==============================
#the affected share
[SHARED]
   security mask = 2777
   create mask = 2775
   directory mask = 2775
   comment = SHARED
   path = /shared
   writable = yes
   printable = no
   public = no