Have you just had the regular patch update before this happened? I'm asking because my L830 received and downloaded it a couple of days ago and it didn't begin the install, the phone switched off and remained dead for 36 hours despite having 2 fully charged batteries swapped into it, connecting and disconnecting the charger, attempts at soft reset. Nothing worked so I gave up and went back to my back up Android phone. On the 3rd morning I plugged in the charger, switched it on and the phone came to life immediately and began to install the patch update! This is happening with every update I've had for the last six months and the time my phone is dead gets longer every time, hence switching to the Android. I can't rely on the Lumia as my main phone now. I hope yours wakes up soon. Fingers crossed