guys, i had the same problem and now i think that is running just fine.

1st, if you have any shield above the screen, take it off! (90% of the proximity sensor problem come from that)

2nd remove the battery for MORE than 15sec, after that, press and hold power key / camera key and whatever key to make shure that ANY power were drained out

3rd put battery again and turn on the phone.

4th IF you're using any "xingling - china/ebay/ etc" battery, swap for the original (i don't konw if it really make any difference but, i did it too)

ps: i heard programs like "Shortcut" cam mess this sensor. If you have it, uninstall it as well.

i did it and worked for me. now, 100% ok both proximity and turning.