Has anyone else had an issue with the proximity sensor being oversensitive? If I'm in a call, I normally hold the phone in my left hand. If I unlock the screen then try to do anything with my right hand, the screen goes black. The proximity sensor seems so sensitive that just a finger 3-4 inches above the top-right quadrant of the phone will set it off. I haven't had this problem with other phones; is it just me, or are others having this issue too?