I've been trying to get my friend's wireless router as locked down as possible, but for some reason when I enable MAC address filtering, she can't access the network at all. She's using 2 Apples, an iBook with an Airport card, and an eMac with an Airport Extreme card. The router is a Linksys 802.11b (can't remember the model # offhand).

She's tried the latest patches for both the Apples, and I've tried the newest firmware for the router, but it doesn't seem to have done anything in the area of MAC address filtering. Also, for some reason, the Airport extreme card can't deal with the DHCP, so I've had to configure all the clients on the network manually (no big deal, but mildly annoying).

Does anyone have any ideas why this might be happening? I've had no luck on google, Apple's website, or talking to Linksys techs. I'd really like to add that last lockdown though its already not broadcasting SSID, using 128-bit key, and obviously no DHCP or remote management enabled.