WP7 what is E_FAIL

Question

I'm using AudioPlayerAgent to build music application on Windows Phone 7. However, when handle OnPlayStateChanged event in the agent, I usually receive E_FAIL error when handle TrackEnded event

case PlayState.TrackReady:
     player.Play();
     break;

So what is E_FAIL and how to deal with it ? Try catch is not a good solution here