[Samba] MYOB Performance issues on Samba

[Lawrence Cruciana]

I am experiencing a performance issue with MYOB accounting package being 
served from a Debian 2.4.18 based server running samba. Clients are 
Win2K/WinXP clients in a small workgroup environment, all maping drive 
to samba 'data' share. Network is pure TCP/IP, no other (MS or Samba) 
servers on LAN.
I've experimented with Oplocks and veto oplocks but to no result the 
performance of the MYOB application on the client workstations remains 
very poor whenever more than one user is connected.
smbstatus returns an Oplock value of 'EXCLUSIVE + BATCH' when only 1 
user connected  - when performance is OK.
Whenever >1 user connected smbstatus returns an Oplock value of 'NONE' 
for all MYOB related files (*.MYO, *.FLK)

Has anyone else experienced this or similar issue with MYOB?
Any ideas?

Below is the samba configuration:

*Note commented sections have been tested but failed.

# more /etc/samba/smb.conf
[global]
   kernel oplocks = no
   default service = data
   workgroup = office
   server string = %h
   load printers = no
   invalid users = root
   log level = 7
   log file = /var/log/samba/log.%m
   max log size = 10000
   syslog = 2
   security = share
   encrypt passwords = true
   socket options = TCP_NODELAY

# --- Browser Control Options ---

   local master = yes
   os level = 31
   domain master = yes
   preferred master = yes

# --- End of Browser Control Options ---

   dns proxy = no
   preserve case = yes
   short preserve case = yes
;   unix password sync = false

   passwd program = /usr/bin/passwd %u
   passwd chat = *Enter\snew\sUNIX\spassword:* %n\n 
*Retype\snew\sUNIX\spassword
:* %n\n .
   obey pam restrictions = yes

#======================= Share Definitions =======================

[homes]
   comment = Home Directories
   browseable = no
   writable = yes
   create mask = 0775
   directory mask = 0775

[data]
        path=/data
        browsable = yes
        guest ok = yes
        volume = data
        writable = yes
        locking = yes
        create mode = 0775
        directory mask = 0775
        share modes = yes
#       public = yes
        hide files = /*.java/*README*/
        case sensitive = no
        map archive = yes
        map system = yes
        map hidden = yes
        #delete readonly = yes
        dos filetimes = yes
        oplocks = Yes
        level2 oplocks = Yes
#       fake oplocks = Yes
#       veto oplock files = /*.myo/*.MYO/*.flk/*.FLK
*