CoreAudio and Airfoil

[niall]

I use Rogue Amoeba's Airfoil product to redirect all sound output from my Mac to an Airport Express network; this works perfectly for my other apps.

However, when Airfoil is running, and I try to start a Windows XP guest in VirtualBox, I get an error that the host audio device is not responding. VirtualBox then uses the Null audio device and consequently I get no sound output.

When Airfoil is not running then virtual box correctly uses CoreAudio and I get sound from Windows locally.

Has anyone run into this problem and could suggest a fix?