Some iPhone 4 users have reported problems with proximity sensor, more precisely, the sensors were working incorrectly and when the respective persons held the phone to their ear, the screen did not close automatically and the persons pressed the phone screen with their cheek and ended calls. Apple promised a solution for this problem, a solution that should be available in the new iOS 4.1, but 2 days ago a spokesperson for Apple Australia recognized the fact that for now there is no viable solution to solve the problem. It's hard to believe that Apple Australia is aware of everything that happens in the US and I doubt that Apple would not have a "fix" in the works now.
I personally have not encountered any problem with the proximity sensor, not even after installing InvisibleSHIELD, so I can confirm that this problem only occurs on certain terminals, not all.
