Take a look at Re: Disturbing Windows 2000 Caching Problem Message #669887.

>It has come to my attention ( KB#293793 and KB#129202 ) that on peer to peer networks running a Win2000 or XP server a process called Opportunistic Locking is running by default. This basically "locks a file, performs read-ahead, write-behind, and lock caching" as long as no other machine on the network attempts to open the file. If someone else opens the file the redirector 'must invalidate cached data, flush writes and locks, and release the oplock, or close the file.' During this process there is 'potential to cause lost cached data on some networks, particualrly wide-area networks'. Not only that,if the server loses track of which files are open it will result in a blue screen of death.
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>Have any of you encountered this problem- either the blue screen of death or data that just disappears. The fix that Microsoft gives us requires editing the Registry. Any information or feedback will be greatly appreciated. Thanks.