They changed the function of one of the audio session type names. Apps need to be updated to use the new session name.
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Apple changed the way the AudioQueue works in 2.2, so that it suspends playback when your iPhone sleeps (shuts the screen off).
Fortunately there is a way to change your code easily so that your AudioQueue will continue in sleep mode. For any developers reading this forum- mikeln at iPhonedevSDK forums figured it out...
The default audio session for 2.2 has changed from:
kAudioSessionCategory_MediaPlayback
to
kAudioSessionCategory_SoloAmbientSound
It looks like programmers have to set the audio session as MediaPlayback explicitly, where previously it was assumed.