In Mac OS X 10.0 through 10.2.8, the option "Wake for network administrator access" (also known as "wake on LAN" or "using a magic packet") in the Energy Saver preference pane only works for Ethernet ports. This is expected behavior. This option does not allow the computer to "wake" for network traffic directed to an AirPort Card or to a modem. The "Wake on ring" option provides a similar feature for modem activity.
Note: You can select this setting even if all Ethernet port configurations are deselected in the Network preference pane.