airplay fails from iTunes 10.2.1 to airport express

I'm not sure if this is a 10.6.7 issue or an iTunes 10.2.1 problem, but when I select airport express to stream music to it, it seems to switch over to airport express but the music keeps coming out of my computer and not the speakers the airport express is hooked to. Yet with Airfoil I can do the same thing and it works fine.