No audio on iOS app using the RemoteIO AudioUnit when the iPad is restarted

I have a strange issue where an iOS app that I have developed works fine when I build and run it from XCode on the device. However, on restarting the device and running the app, I get no audio at all. If I subsequently kill the app and restart it from the device, I start getting audio again. I initially thought it was an Interruption Handler issue, but am not sure any more. Any help would be appreciated!

Here's my interruption handler just in case.

static void MyInterruptionListener (void *inUserData,
                                UInt32 inInterruptionState) {

printf ("Interrupted! inInterruptionState=%ld\n", inInterruptionState);
pediViewController *pediController = (__bridge pediViewController*)inUserData;
switch (inInterruptionState) {
    case kAudioSessionBeginInterruption:
        CheckError (AudioOutputUnitStop (pediController.effectState.rioUnit),
                    "Couldn't start RIO unit");
    case kAudioSessionEndInterruption:
        // TODO: doesn't work!
        CheckError(AudioSessionSetActive(true),
                   "Couldn't set audio session active");
        CheckError (AudioOutputUnitStart (pediController.effectState.rioUnit),
                    "Couldn't start RIO unit");
        break;
    default:
        break;
};

}

The issue went away on upgrading to iOS 6. I did some intensive debugging by commenting out each and every line of code in the audio callback and testing by restarting the iPad and running the app again 3 times each. Finally it was solved by updating to iOS 6 on the device and running on that. I also got a huge performance boost in doing so!