Problems setting up security on wifi network

Hi all
I am trying to secure a small wireless network.
It consists of mainly macs with one PC and a Mac Mini acting as a server
We use a Netgear DG834g router.
I am trying to secure the network starting with enabling the access list
I started by turning all the machines on to produce a list of available stations.
I then moved them onto the trusted wireless stations list and clicked apply.
However when I tried connecting files on the server I got the message.
"Unable to find file on server or server not present".
The router seems to be working fine and I am wondering if this is a network config problem
If someone could give some ideas as to what I might be doing wrong I would be very grateful
Best regards

YOu should run WPA security with 128 bit password.
Don't worry about mac address filtering, it is useless.
THen of course secure your ports to the WAN