this is a short howto to setup a working connection which can be established with 802.11b AND 802.11g clients
with MAC Filtering, and a Shared WEP Key

to clear some things out, the 802.11g will work at 54MBit in this configuration it does not drop back to 11MBit.

some given things:

SSID: AAPg (alter this to your needs)
WEPKEY: 9F062FF8D6CA11039801585A09 (alter this to to your needs MUST be 26 characters may be characters which may be used: 01234567890ABCDEF.
MAC: 00-11-22-33-44-55 (alter this to the mac address(es) of your wireless NIC cards)

below you find screens, edit your router config according screens below.