i got this phone two weeks ago. i would be in the middle of doing something and then the screen would fade blue and turn black and it would be a glowing black screen and i would have to hold down the power button for it to restart itself. i took it back to the metro pcs store and they gave me a replacement one. the new phone was fine for about a day, and then it started doing the same thing. i dont have advanced app killer or many other apps installed. help???