Created Issue: System.NullReferenceException in NAudio.Wave.WaveOutEvent.PlaybackThread() [16386]

I have written an application that uses nAudio to play wav files when 'events' happen, and records audio from the microphone.

I am occasionally getting a System.NullReferenceException from NAudio.Wave.WaveOutEvent.PlaybackThread()

I am using nAudio 1.5.4.

Any thoughts on what causes it, and how I can resolve it?