This just happened to me:
Had Amazing Weather on the screen
Placed phone on wireless charger
then turned off the screen
a little bit later I got a text and when I tried to turn my screen back on it wouldn't come up.
I tried removing it from the charger and connecting it to PC, not screen.
I tried calling my phone and it rang, but I couldn't answer it because screen was black.
I tried the brick reset that I saw on here and finally got it back running without doing all the software updates.
So, I pressed volume down and then the power button and held them until the phone vibrated (about 5 seconds)
I then pressed volume up and lo and behold the AT&T logo appeared for a second and then I got the gear and lightening bolt screen for a while.
Nothing was happening so I did volume down- power button again and the phone rebooted and is working now.
I just installed the portico update earlier today.
I don't know why phones that are designed without a removable battery don't just a have a hard reset you can hit with a paperclip or something. Phones are going to crash hang sometimes. It is just a fact. I have had to jump through hoops and figure out how to recover an iphone and an ipod that crashed and now my Lumia 920. When my old Blackberry crashed, all I had to do was a quick battery pull and problem solved. Just own up to it and give us a hard reset feature.