[Samba] Oplocks break and no route to host problems

[xavier]

Hi,

I' m experiencing many problems with oplocks break failure and Error: no 
route to host.essentialy onto \profiles dir and \netlogon dir.
So My clients cannot update many files on the SAMBA/PDC and cannot read 
the NTconfig.pol file to update their policies.
I have many PC that are old computers with Win2k and have an Antivirus 
and are slower machines ...
This problem less occurs on newer machines.
I have seen searching the web that I may disable oplock (oplock = False) 
into the smb.conf and "level 2 oplock" too.
I don' t now if my default configuration have this parameter set cause I 
don't see it into my smb.conf.
But perhaps I can play with a delay parameter that I could but bigger, 
is it possible ?
I would like to now if there is a solution to test in a good way this 
problem.
thanks

My configuration is :

Samba 3.0.20 under Linux Mandrake 9.2
compiled with acl and quotas support under an XFS filesystem working great.
recycle and vscan/clamav modules compiled with but not enabled on all 
shares (disabled onto \netlogon and \profiles)

Xavier