There is something quite FUBAR about AirPort Utility...
Here's what works for me when AirPort Utility gets stuck on reading an Express' configuration:
- Unplug AirPort Express from the wall power outlet
- If connected to DSL or a network switch, unplug the ethernet cable
- Plug in AirPort Express, and wait until the LED blinks amber
- Run AirPort Utility only after you get the amber LED blinks
- You should be able to connect to your AirPort Express and modify its settings
There are several threads on Apple Support Discussion Forums about how AirPort Utility gets confused when the AirPort Express is assigned a new IP address from DSL.