Hard to say. Marctronixx and I show that with a proper MHL adapter and a native 1080p TV, 1080p works via MHL. Clearly your TV is not in question. But you also mentioned a problem with the international One X (Harry's phone for those that don't know) having a 1080p MHL issue. Maybe you could try another adapter and the shop would let you return it if it's a One X software issue?