My Nexus 4 shut down on its own while in use, and refuses to start up again. I've tried holding down the power button for various durations as well as trying to start it with the power plugged in, to no effect. I see the charge LED staying on continuously. I am running stock android on the piece and had received my 4.3 update quite a while ago. Any ideas as to what the problem might be and how it can be rectified?