Did you upgrade to iTunes 10 and discover that when you connect to your AirTunes what once was normal volume levels are now non-existent? I spent days trying to find out the problem.
I would connect to my AirTunes like I normally would but I would have to turn the volume up on the amplifier all the way just to hear my music (well, barely hear it). Turns out Apple introduced some volume control panel in iTunes and by default the volume of AirTunes is almost all the way down, wtf?
Down the bottom of your iTunes (beside the genius icon) click the speaker selection button, then select multiple speakers from the menu and then adjust the volume of your AirTunes accordingly, problem fixed.
I don’t know why Apple changed the way volumes are handled, but they could have at least made it a bit more known.