The unimaginable happened to my Nokia Lumia 1020 this morning when trying to launch the ESPN ScoreCenter app from my start screen. I’m not sure what might have caused the lockup, but whatever it was made the screen freeze in that state. I tried holding down the power button for 10 seconds but that did not work.
After doing some research online I discovered a way to reboot the phone when it freezes up. This applies Windows Phone 7 devices as well, it’s not restricted to Windows Phone 8.
How To un-freeze (soft reset) a locked-up Nokia Lumia 920, HTC 8X, Nokia Lumia 620, or any Windows Phone device
Simply hold the lock button and volume down button at the same time for 5-10 seconds. Once the phone reboots you can now get back into the operating system and make sure everything is normal.
This should not affect your settings, messages, photos, contacts, etc. This function simply reboots your phone without forcing you to do a backup, although it’s highly recommended to back up your phone often.
If this method doesn’t work for you then you might have to deal with Nokia’s warranty department or whoever you bought the phone from. After performing this simple 2-button combo my phone rebooted and all has been well since.
I first read this tip at ukmobilereview.com.