Ok, I know the screen goes black when you use the phone because of the sensor. But say I'm on the phone and I need to use the keypad for an automated system. Normally, the keypad pops right up when I take my face away. Lately, when I take my face away, the screen is locked and I have to put in my "design code" to unlock the screen and get to the keypad. I know the phone doesn't normally do this, cuz if I reboot the phone, it works like before. For a while. Anyone know what causes this?