[Samba] Samba locks the file, Linux user brakes the lock with opening the document

[Maris]

And the situation is following
I have Lin server + XP user + Lin user.

1.Xp user opens water.xls via Samba
2.Samba locks the file.
3.Lin user opens the file water.xls after 20 seconds via NFS.
4.As Samba has locked the file, Lin users see (water.xls READ ONLY)
SO far seems everything is working really FIne.
Problems start when we go further on.
5.Lin users after 5 minutes tries to open water.xls to edit it, in the same
time XP user is still working with it.
6.Lin user opens water.xls and it is WRITABLE. , however XP user still
edits  it.
7.The result is corrupted file, not saved file, information lost for XP
user, time lost for XP user.
What happened?

Problem:
Samba locks the file fine, however after one Lin user try to open the file
lock is broken by Lin user. So next time Lin users opens the file – file is
not locked, because samba lock ir broken.

You can also read this post here:
http://www.linuxquestions.org/questions/showthread.php?p=2312691#post2312691

is there any help available?
-- 
Maris Dembovskis