[Samba] Slow MS access

[Max]

Hi,
I have samba-3.0.11-1 on a Red hat ES 2.1 box.
I also have a Win 2003 Server Domain Controller, to which my users should
autenticate.
My files are all in linux machine (+ also apache, mysql etc)
I have also an Access mdb that could be open by several user at same time,
based on linked mysql tables.
Opening certain masks in access is veryyyyyy slow, so I try to create
another share, accessible from everyone, and put there the same db. Well,
this way Access works fast. 
I'd like to know which is the reason for the performance difference.

Here my samba conf
Thanks

# Samba config file created using SWAT
# from 0.0.0.0 (0.0.0.0)
# Date: 2005/02/18 18:57:26

# Global parameters
[global]
	level2 oplocks = No
	lpresume command = lpc release '%p' %j
	remote announce = 10.243.255.47/mydomain
	printing = lprng
	dns proxy = No
	hide files = /*.GID/*.gid/*RECYCLER/desktop.ini/DESKTOP.INI/
	encrypt passwords = yes
	queueresume command = lpc start '%p'
	socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
	max log size = 1000
	directory mask = 02770
	admin users = administrator
	preferred master = No
	lock spin count = 100
	security = DOMAIN
	ldap ssl = no
	printer admin = administrator
	queuepause command = lpc stop '%p'
	lppause command = lpc hold '%p' %j
	server string = Server Dell
	workgroup = MYDOMAIN	
	message command = /bin/mail -s 'messaggio da %f on %m' root < %s; rm
%s
	lock spin time = 200
	log file = /var/log/samba/log.%m
	netbios name = DELL_ES
	create mask = 0664

[archivi]
	path = /home/ei
#	valid users = +mydomain
#	write list = @mydomain
	read only = No
	guest ok = No
#        oplocks = Yes
        level2 oplocks = No
#	veto oplock files =
/*.mdb/*.MDB/*.dbf/*.DBF/*.pst/*.PST/*.dat/*.DAT/*.idx/*.IDX/*.vix/*.VIX/

[test]
	path = /home/test
	writeable = yes
	public = yes
	guest only = yes