It's been a while since I used the Airport Utility. Today I went to add a Airport Express to my wireless network so that I could play ITunes on my Bose system wirelessly. When I tried to hardwire I got an awful buzzing sound, so I decided to try it wirelessly.
The problem: When I opened up Airport Utility I got:
You can't open the application "AirPort Utility" because it is not supported on this architecture.
I believe this happened as a result of Leopard install, but I'm not sure because it's been so long since I actually opened up the Airport Utility.
The solution: Go here and install the latest Airport Utility. http://www.apple.com/downloads/macosx/apple/application_updates/airportutility541.html