I have fixed my proximity sensor and can now make calls without hanging up/muting etc. I was having severe problems with the proximity sensor on my iPhone 4. During calls my ear was hitting mute, end call, face time etc. Today I had the hardware replaced at a retail store and restored a backup. The problem remained. Then I read a post on this site suggesting resetting the network settings and thought, why not, Apple had no fix. Before I started I tested and recorded that the proximity sensor required my hand to be about 5mm above the sensor before it kicked it and blanked the screen. Then I used Settings/General/Reset/ Reset network settings. After this the proximity sensor worked at about 3cm under exactly the same conditions. I have continued using the phone including setting my wifi password which had been cleared. I have no more problems. This wont clear everyone's problems but: As it takes 30 seconds and doesnt wipe your phone, give it a try before sitting on the phone to Apple, driving to the Apple store etc. Besides they dont have a fix yet. My testing pretty much proved that for me, changing hardware didn't help but a configuration change did. Therefore even though other users may have other setting, which in combination with a complex bug mean this fix doesn't work for them, it is a software bug in some cases, probably most. So Apple should work this out in the end and post an update to the OS. If this fix doesnt work for you and you want to do something, test your sensor by starting a call, leaving the speakerphone off and putting three fingers over the top of the phone covering the entire phone above the screen. If the screen blanks when your hand is close but comes on when less than a couple of centimetres away, then see if a software fix helps. Take a backup and then wipe the phone and then retest. Let us know your results here. It may help others, including Apple. And they need a little help testing but find me a developer that doesn't. Good luck.