My son has an Airport Extreme base station and it is working nicely with a cable modem. I bought him and iPod and an Airport Express base station, mainly for use with iTunes and his home stereo. I can configure the AE to work as a separate base station connected to the cable modem and to his stereo and he can surf and play iTunes through the AE 'Airtunes'. If I configure the Extreme base station as a 'Master' and set up the AE to connect to an existing network all goes well during setup but when I try to select the AE for Airtunes in iTunes I get a message that reads, 'The remote speaker "Carl's Stereo" is currently being used by someone else. Please select another speaker from the menu at the bottom of the iTunes window.' There are no other speakers in the iTunes menu!! I have reset the AE several times and have gone meticulously through the Airport Setup Assistant. Always same results. Only one computer--iMac G5 17", one cable modem, one Airport Extreme base station, and one Airport Express. Looking for help. Ray Reedy