I have had a similar problem. I replaced my lcd screen. Everything related to the screen worked fine but the proximity sensors were not working. I figured it was just a poor connection so I took the phone apart and reconnected the ribbons. I did this without disconnecting the battery and the battery was charged about 8o%. When I turned it back on the lcd screen worked but was VERY dim. Have I shorted something out? Is there a solution to this problem? Any ideas?