[Samba] OSX Server - Excel files

[Hugh Evans]

Hi, I am new to this list, so please excuse any redundancy in my 
question.

I have 60 Windows XP users who are tied into three Mac OSX File - 
Xserve file servers. There is one big problem - ... we are having 
issues with Excel files, that on occasion, are not being recognized, 
taking literally minutes to load and other quirky abnormalities. Excel 
on the XP desktop machines will refuse to save documents back to the 
file server - though Excel can still browse, load and save other Excel 
files. This is not happening all the time - maybe once in every five 
access'

I posted to a Mac server mail list but had little respone. - one person 
suggested turning off "opportunistic file locking" on smb. Can somebody 
advise me on how to do this... from the command line if necesssary

It seems that his would be a pretty draconian solution  - Has anybody 
else seen this kind of behaviour? Any other possible causes / fixes?

Any help would be appreciated.

Hugh Evans