If you have upgraded to the latest NetShield (4.5.0 SP1) on a Win2k Server and you discover that you now have slow network file access e.g. any Microsoft Word and Excel document takes anywhere from 20 seconds to open from a network share. I have noticed this only with Windows 2000 Pro and Windows XP Pro. If you have Windows 9x they might not be affected. If you disable the McShield scanner the problem evaporates û this is great apart for the fact that you have no on-access scans taking place. There is a workaround and it does not lie with NetShield but with Microsoft. It seems to be the work of opportunistic locking and the way it works with the McShield scanner. Disabling the granting of opportunistic locks solves the problem. For detail you might want to consult the following Microsoft Knowledge Base Article - Q296264.
You then reboot the server and hey presto !! much improved network access. An important thing to remember is to back up your registry before attempting to edit it. This problem might be cleared up by a future hotfix or service pack. I hope you find this informative.