AirPort Extreme allowing wireless but not ethernet connections

Good afternoon,

I have a Time Capsule as the main router in my house. I also have an AirPort Extreme which connects to this via wireless using the 'Join an Existing Network' choice in Airport Utility.

Recently I have not been able to connect to my Airport Extreme via ethernet from any of my computers. I have a MacBook Pro, Mac Mini and Windows 7 PC. All of these computers connect to the network fine via wireless.

I have tried connecting my MacBook Pro directly to my Time Capsule via ethernet which seem to work fine. This leads me to believe that it is a problem with the settings that the Time Capsule is feeding the AirPort Extreme, or on the AirPort Extreme settings themselves.

This is a screenshot of the Network preferences panel on my MacBook Pro OSX SL.

As you can see, the Ethernet connection is reporting a Self-Assigned IP.

Running a quick troubleshoot on Windows 7 gives this error.

These errors are very similar and therefore leads me to conclude that my AirPort Extreme is not correctly assigning IP addresses for connected clients.

I have searched a few forums and most have said that Renewing the DHCP Lease through AirPort Utility and Network preferences can sometimes solve the problem. This has unfortunately not been the case with me.

Can anyone suggest a solution to this problem? Is anyone having a similar problem?

Thanks.