I got a new unlocked at&t samsung focus last week and updated to mango. Now the problem i am facing, whenever i receive a long duration call (say for instance for more than 5 minutes); when i remove the phone from my ear to end the call, the screen does not show up, display remains off (maybe the proximity sensor issue or something). I have to press the power button to invoke the display and end the call afterwards. For trial purposes, i tried making a call and playing with proximity sensor with my hand, it turns on and off flawlessly. Any ideas why this is happening ?