“So I have some other updates. We’re tracking some problems with the proximity sensor and we’re working on it.”
iPhone 4’s proximity sensors is designed to sense when the phone is held up to the user’s face and it turns off/deactivates the display, thus helps in avoiding unintended input. But some of the iPhone 4 users reported unintended call ending and key pressing.
There’s no word on when the firmware update with Proximity sensor fix will be releases.