I had the same problem and was not told about the hard reboot by Tech Support or I would have tried it. My 920 quit after 3.5 weeks in my hands, When it locked up I turned it off, but it would not come back on. Since the phone is unresponsive to the charger, doesn't detect the phone and it will not vibrate at all, I tried for a warranty replacement with very bad results that I wanted to share with this forum; message below. The story has a happy ending because an ATT Executive Care Rep helped get a phone shipped to me. I am very, very accurate in my observations below and ATT is making headway in improving service. Thanks everyone, I should have checked this forum first.
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Problems with AT&T Wireless Warranty Service
Order Details DATE ORDERED: 12/17/2012, Item Status: Processing
Order Date - 12/12/2012Order Status - Cancelled All of your items were cancelled and will not be shipped.
See information above on the order status for warranty replacement of my NOKIA 920. I purchased the phone from AT&T Kiosk on 16 Nov. Twenty Six days later the phone died while I was trying to access my email, screen locked up; after turning phone off, I could not turn it back on. I’ve done everything possible and used AT&T Technical Support to try and resolve problem—no luck, I think the battery is defective. I am a DoD contractor with 11 years customer care experience providing IT Services. I’m writing you to bring a couple of issues to your attention and to see what your expectations are for the replacement of my defective phone.
1st Issue. No follow-up by customer care or the warranty department on the status of my first order. After 4 days the online status displayed “processing”; I had to call Sunday evening to see when I could expect my replacement. It was backordered, but status was not updated. Kind lady at customer care, competent and thorough, acted to talk to warranty dept. manager and found the phone was not on backorder (maybe they were referring to blue phone and not a black one). She booked a call back with me Monday after 5pm but failed to give me update. Online status now showed cancelled. I have made at least 8 contacts to warranty dept., order status chat, and customer care over the past 2 days. Here is where you need to focus….
NOT 1 follow-up call or email was made to me—this you did wrong. At least the customer care gal had the right attitude and tried to do right by me. When problems need to be escalated, they are probably better handled by Customer Care, someone skilled (with permissions/access) to do something for the customer. Sorry, she did not continue with me—I’m sure it was because of the problem you are having with NOKIA and the fulfillment of on warranty phones for the 920.
2nd Issue. Backlog, backorder, and lack of fulfillment on Nokia 920 devices. I doubt that I need to say much about this. I talked with the warranty dept. supervisor, Nicole, and she gave me a good deal of info on why things were happening like they were. I was told about 20 days ago, you had a backlog of about 300-400 phones and Nokia was maybe only shipping 100 phones to you at a time. Since then the backlog is better, but you obviously still have an issue with Nokia—good luck. FYI, I was also told the “back room” was cancelling orders because they knew they would be fulfilled in time (what wrong with this picture)
Final question. Where are we on my order, 3-5 days; no one can tell me when. From my experience, I’ve always tried to set expectations with clients—you see I’m also 27 year retired Air Force person who feels people have a right to know what’s happening. I like the fact that Nicole at least gave me the back story—at least I know she is genuine which I value the most.
helped me alot, didnt have my phone for even a week and just randomly turned off and wudnt start, almost had a heart attack lol thank you very much!!!!!
Help Lumia 920 Will not power up after text a friend my Nye 920 it died !!!!!
Thanx for hint now after hARD Reset my Nokia 920 start op 
