I have two second gen. Airport Express configured to join my (non Apple) wireless network. Their only use is as AirPlay audio outputs. The units themselves function fine, (confirmed by playing audio from my iPhone), but on my iMac I am now unable to switch audio output to either of the boxes from, for example, my bluetooth headphones by clicking on the menu bar speaker/sound icon and then selecting either of the Airports, and the weird thing is it causes the internet connection to my Mac to be interrupted. Selecting either of the outputs from 'Output' under 'Sound' in System Preferences DOES work, and does not break my network connection.