I was looking through our resorces about what might be going on here and found a great article for troubleshooting that flashing amber light. It is called Wi-Fi base station: Understanding and resolving a blinking amber status light and you can find it here: http://support.apple.com/kb/TS1589.
How to resolve a blinking amber status light alert
Launch AirPort Utility to determine why your Wi-Fi base station status light is blinking amber. Apple recommends that you use AirPort Utility 5.5.2 for Mac, AirPort Utility 5.5.2 for Windows, or a newer version of AirPort Utility if one is available.
- AirPort Utility 5.2 or later opens automatically if your Wi-Fi base station requires your attention. You may also choose to launch AirPort Utility at any time.
Do not use any version of AirPort Utility earlier than 5.0.
In Mac OS X, AirPort Utility is located in the Applications > Utilities folder.
In Microsoft Windows, AirPort Utility can be located by clicking Start > All Programs > AirPort.
Note: You may also locate and download the latest Wi-Fi base station firmware and software by clicking here.
- In the AirPort Utility window, locate your Wi-Fi base station and double-click on it to open the Summary window. Note: If you have more than one Wi-Fi base station, double-click on the icon for the Wi-Fi base station that has the amber circle next to it.
- When the Summary window appears, double-click the amber circle to the right of Wi-Fi base station Status to open the Status window.
- The Status window lists any conditions that require your attention. Respond to each item until there are no more items listed.
Important: You must reset the Wi-Fi base station using the reset switch to re-enable checking for the conditions you ignored.
- Eliminating the blinking, amber status light may require making changes to a specific setting, or putting a checkmark in the "Ignore" checkbox beside any option you don't wish to change. A checkmark simply tells the AirPort that you are aware of the issue and you have chosen to ignore it. For example, you may wish to leave your AirPort open without a password so that anyone can join your wireless network.
- Click Update to apply your changes (the Wi-Fi base station will restart).
- After the Wi-Fi base station has restarted, the status light should be green and not blinking. If the status light stays amber in color and blinks after the Wi-Fi base station restarts, you may repeat the steps above.
- AirPort Utility 5.2 or later opens automatically if your Wi-Fi base station requires your attention. You may also choose to launch AirPort Utility at any time. Do not use any version of AirPort Utility earlier than 5.0.
I've been searching for the answer to this, too. I've been through all the steps that the troubleshooting article recommends, many many times, to no avail. Searching the threads on this site, I haven't found an answer that wasn't just replacing the unit. I have tested the modem, can connect directly to it with my computer, have swapped and tested the cables, and everything works except for these error messages from the Airport Extreme.