I have the Straight Talk LG 511C phone also. My touch screen all of a sudden stopped working. Then it started back working but it's not working correctly. The calibration is off. I tried to reset the calibration but every time i touched in the little box, it would say that I'm out of range. I have tried everything from taking the battery out, to letting the phone go dead and then charging it back up. I also tried scraping the side of the screen to try to get lint and other debris out, but that did not work either. My keyboard is working, but I am not able to get to my contacts, pictures, or anything. Can anyone help me please? Thank you.