How do I fix "core audio is not available" in GarageBand?

Are you opening a project that came from from another computer with a different GarageBand version or other JamPacks installed? Or are you creating a new project?

I got this message about 5 times in a row on my new iPad on iOS 6 - from just opening the demo that comes with GarageBand.

I tried to record audio but it failed to record anything. The controls were slow to respond and basically unworkable. I had to shut it down.

Killing the app and restarting fixed it.