When the Instant Hijack component is installed for Airfoil, Audio Hijack Pro, or Nicecast, they can generally grab audio from applications that are already running. However, on Mac OS X 10.6 (Snow Leopard), hijacking of some applications still requires that the application be restarted even when the Instant Hijack component is installed. When hijacking Safari, QuickTime Player, and certain other sources, you'll see a message like this:
As indicated, the hijacking application (in this case, Airfoil) must quit the source (in this case, Safari) to force it to restart in 32-bit mode. Once that's done, Airfoil will be able to grab audio from these applications.
Workarounds
There are two fairly simple ways to work around the need for these applications to be relaunched into 32-bit mode. Both require Instant Hijack to be installed, of course.
Force 32-bit Mode:
First up you can force any application, such as Safari or QuickTime Player, to run in 32-bit mode. To do that:
1) Make sure the application (we'll use Safari) isn't running. Be sure to Quit Safari, don't just close the windows.
2) Go to your Applications folder and right-click (or control-click) the Safari icon and select "Get Info".
3) Check the box that says "Open in 32-bit mode".
4) Close the Get Info window and relaunch Safari.
Now, whenever Safari launches, it will load in 32-bit mode and be hijackable instantly, with no restart required.
Use a Secondary Browser:
Alternately, if attempting to hijack web audio via Safari, you can instead use a 32-bit browser such as Firefox. Setting Firefox as your source and playing your audio there will enable its audio to be hijacked without needing to relaunch the browser. To learn more about Firefox, and download it for free, visit the Firefox website.