Security

I am at my wits end. A few months ago, my Windows 2000 server stopped letting wireless clients into it’s folders. It happened all of a sudden, like it was tied into a security patch update or something. If you are hard wired to the network, everything is fine. If you are wirelss, the 2000 server ONLY will not let you into it’s folders. It doesn’t seem to matter if the laptop is running Windows XP home or Pro. This is a problem since the engineering folders are on this server. Has anyone heard of this or heard of a patch that has a problem like this? I have had a couple f companies look at the problem and spent a couple of thousand dollars on it to no avail. Help!!!