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Try performing a hard reset:
1. Turn the phone off. If it won't turn off, take the battery out then put it back in.
2. Open the physical keyboard.
3. Press and hold the Power + R and Space keys.
4. The recovery screen will appear with a yellow exclamation point. Press Z and M together on the keyboard.
Now you'll lose all the info which isn't saved to SD card. All your contacts should already be saved to your google account so they should be safe as long as you remember your login info.
Let me know if you have any questions, also, please remember to click 'accept' before logging off. Thanks
That sucks, you've got a software problem on your hands. You can try the same steps with the phone plugged in via USB--but the phone will most likely need to be flashed. Verizon does offer phone flashing for most of their phones so unless you have a different carrier, I'd take it by there and have them flash the OS on it. If you don't have Verizon, then take it back under your 12 month warranty (if applicable). There's really nothing you can do to make it boot up besides flashing the phone I'm afraid.
Please don't hesitate to ask me if you have any questions, also, even though you've posted a deposit, you still need to click 'accept' if you have no further questions.