Unresponsive letter R on my touchscreen

Ok,

I have a dead spot where the letter R is on my sons iPhone 4 gsm. It is the same spot on the screen that apple has designated for turning on and off wifi, etc. flip the screen over and it is the U that is dead.

I just put a brand new complete front screen on it and the dead spot is still there. Anyone have any ideas as to where to look or what to do to area to troubleshoot.

I have done a full software restore through ITunes

I replaced the screen

I haven't tried throwing it yet, ha ha

Any ideas?