[Samba] Oplock problems

[Charlie Leach]

Dear all,
 
I am new to this, I apologise if I am using this list improperly...
 
I'm experiencing an oplock problem since installing windows 2000 service
pack 4. 
The problem was not solved by upgrading from Samba 2.2.3a to 3.0.0 rc4
 
When I open an excel file from the windows environment no oplock is
activated. This causes the problem that when I save the file I get a
standard "do you want to overwrite" dialogue. Once the file's been saved
once, the oplock kicks in "EXCLUSIVE+BATCH" and all is fine. (MS Word
doesn't have the problem).
 
I don't understand how oplock works, and why it's not locking the file
to me as a user when I open it, but only when I save it. 
Can someone let me know where I might learn about oplocks or explain
what the problem is so I might solve it?
 
I've got 500 points (maybe more if it's complicated) running on this on
experts exchange if anyone wants to answer it there:
http://www.experts-exchange.com/Networking/Linux_Networking/Q_20749863.h
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Do I need to subscribe to the list to get an answer? 
Many thanks in advance,

Charlie Leach