Airoport Express set up

I am trying to set up a simple configuration where I can transmit iTunes music wirelessly to an Air Port Express unit about 4m away which then conveys the music to a music centre via stereo cable. So no internet link via ethernet, no printer via usb, just plain audio. I have downloaded the latest Leopard-friendly Airport Utility 5.3.2, but after waiting for the Air Port Express unit to coplete its startup routine and getting the flashing amber light, I double click the utility and it is 'unable to find any Apple wireless devices', even when the MBP and Air Port Express unit are close together.

From the manual, I cannot see anything else that I should be doing... can anyone see what I am missing here?

thanks