About a week after Kitkat update my phone started this (still on VZW at the time). It will randomly get stuck with a black screen and the only way to get it back up is to hold the power button and it will do a reboot. Sometimes that reboot is no good and I need to manually shut it down again and restart. I have tried freezing things with Ti with no avail. Since it is random, I am assuming it is an app running in the background or a setting. I have posted a question about other apps to freeze on the string here and am waiting a reply.
Has anyone came across a fix for this issue or has an idea?