This reply is specific to Steve Nicholson's Airport Utility problem:

Go to the following site and download "AirPort Utility v5.6.1 Launcher.app". It has worked like a charm for me on both Mavericks and Yosemite, allowing me to continue using my original 802.11g Airport Express units.

http://coreyjmahler.com/2013/10/24/airport-utility-5-6-1-on-os-x-10-9-mavericks/

It does not interfere with the operation of Airport Utility 6.3.4, which is still necessary to configure the newer Airports.

Cheers.