I'm using Airplay to stream system audio to my Denon AVR-1713 receiver. It shows up in the volume control when I alt-click it, and works great. The problem is, after some time (didn't pinpoint how long), it disappears from the list and I can't select it. Going to the sound preference pane I can still see it there, but if I select it, it reverts back to internal speakers. Restarting my router (Netgear WNDR3700) seems to work, but I don't want to restart my router every time I want to use Airplay. Airfoil always work great, but I don't want to use that when OSX supports it natively. I've found some forum posts with people having the exact same issue with Airport routers, but no fix. Anybody got a clue? It's been like this in 10.8, 10.8.1 and also 10.8.2.