The Apple Airport Extreme by default is set to a wireless security setting called WEP (Transitional Security Network), which is not compatible with the Eye-Fi Card and is also not the standard implementation of WEP. To properly configure your Airport Extreme, please proceed as follows:

Warning: This will reconfigure the security settings for your wireless network. You will need to reconfigure all of the computers on your network to reconnect using the new security settings.

• Launch the Airport Utility and confirm that your Airport Extreme is running version 7.2.1 or higher.
• If not, go to the Aiport Utiltity and select Check for Updates
• Once 7.2.1 or higher is installed, Click on the Wireless Tab
• Go to the “Radio Mode” and select “802.11n (802.11b/g compatible)”
• Go to “Wireless Security” and select “WPA2 Personal” or “WPA/WPA2 Personal”