Hi,
I just ran the SimpleApp untouched and got the same error:
2015-01-29 16:24:16.763 OpenEarsSampleApp[1299:580806] Local callback: Pocketsphinx has stopped listening.
2015-01-29 16:24:20.466 OpenEarsSampleApp[1299:580849] 16:24:20.466 ERROR: [AVAudioSession Notify Thread] AVAudioSessionPortImpl.mm:52: ValidateRequiredFields: Unknown selected data source for Port iPhone Microphone (type: MicrophoneBuiltIn)
2015-01-29 16:24:28.964 OpenEarsSampleApp[1299:580806] Local callback: AudioSession interruption ended.
2015-01-29 16:24:30.519 OpenEarsSampleApp[1299:580806] Local callback: Pocketsphinx is now listening.
The only difference is that the sample app could re-start listening.
Device: iPhone 5 (Model A1429)
iOS: 8.1.3 (12B466)