There's a bug in the linux NFS implementation where it's possible to corrupt files when the server is a NetApp filer and two (or more) clients have write access to the file. A good example of such a file is ~/.zhistory. This has been fixed upstream and on RHEL5:
http://lkml.org/lkml/2008/2/7/642 (second changeset)
and discussed here:
Please apply to the Hardy kernel, and possibly others, thanks!