Surround was working great on my XBOX until today too. As soon as I updated to the new version I only hear sound from two channel videos. All other apps (Netflix, Hulu, Blu-Ray) work just fine. Nothing else changed on my setup. Please fix, this version has problems.
I just commented on this in another post. It seems as though there is no ability at present to select the correct audio track in the mp4 format. It defaults to the aac stereo track, which is great for compatibility on a range of devices but pretty useless for those of us who have a decent audio / home theater setup and can’t access that crucial 5.1 audio on the second track through the xbox app.