My phone is not rooted, never has been. Here is how I have had my phone crash on multiple occasions. First some background. I have custom mp3 ringtone selected for the contacts where this has occurred. And they also have a photo assigned. To create the lock-up / crash I select the contact and hit dial. The phone says dialing. At the same time the same contact calls me. Screen stops responding, power button dead (most times). Only seems to happen when calling contact matches the one I am dialing. Have had others call while dialing and it doesn't seem to crash. A very special set of conditions, but seems to happen once ever couple of weeks.