On Verizon .... About half the time I try to call someone, the screen dims (normal) but then undims and never places the phone call. The fix is to reboot. And after reboot, there is no guarantee that this won't happen again. Just seems like once this happens, I have to reboot just in a hope that the reboot fixes it. Sometimes when a call is placed and it actually says dialing, there is no dial-tone sound and no indication of ringing and no indication that the app is even doing anything. When trying to answer phone calls, sometimes the animation from gesturing downwards goes 90% and the phone app locks. Fix: reboot. Sounds like some sort of mutex hell inside of these apps.