Just noticed this today. Tried searching for it a little bit, not sure if this relates to the proximity sensor problem that's already been noted. I've noticed that during a call, maybe 85% of the time, the home button does not work, the sleep button does not work, and at the top, the "Touch to return to call" also does not work. Touching the screen stills works, I can still open Safari and browse around for example, but the top green portion isnt responsive when touched. So far I've isolated this solely to during the course of a call. Maybe using a Bluetooth is a factor. Just wondering if anybody else has this problem. I've tried resetting, turning phone completely off and restarting.