Airport utility an error occurred while updating the configuration
Unless you have a firmware that supports WDS on your 3rd party wireless router.
The Time Capsule can only "extend" a wireless signal....using wireless only...another Air Port Extreme, Time Capsule, or Air Port Express.
I tested this earlier this morning with a spare USB drive.
It could not be simpler to turn on the Back to my Mac feature in Airport Utility — you literally just type in your username and password.
In both cases, Air Port Utility will happily allow me to set up the Time Capsule and have it join my existing network.
When I go back and tell Air Port Utility to have it my wireless network, the Time Capsule tries to update itself and then just fails.
Airport Firmware 7.4.1 enables the Back to my Mac disk sharing feature announced this week for previous generation Airport Extreme and Time Capsule devices.
I'm trying to get my 2009-era Time Capsule to extend my home wireless network (broadcast by a non-Apple router).
I reset the Time Capsule and Air Port Utility can see it on both my i Pad mini (i OS 6.1.3) and my Mac Mini (OSX 10.8.2).
It seemed/sounded like you just wanted to take the signal, bounce it to the TC then to the Express.
If that's the case it be done, without any extra purchases.Certainly without any addition of a wireless jack extension, which no offense to the individual recommending it, but would be a really silly option in this scenario.