Good news - playback works now. Bad news - the guide is completely broken for me (each channel showing 'no information' and impossible to change the channel when clicking it in the guide itself).
I have the exactly same problem. Sony X900E. Started sometimes in the last week for me (after the app auto-updated itself). Same symptoms - live tv plays for half a second and follows with a black screen (can't watch anything). I'm on 1gig fibre, TV ...