I had the same problems with my iphone 3gs after I replaced a new LCD and tried some everything (powersleepbutton/homebutton method ..)
make sure that a chromepiece on the chrome frame is touching the logicboard on the bottom. the chromepiece and make sure is touching a little copper rectangle/square .
FOUND SOLUTION!!!!!!!
I had the same problems with my iphone 3gs after I replaced a new LCD and tried some everything (powersleepbutton/homebutton method ..)
make sure that a chromepiece on the chrome frame is touching the logicboard on the bottom. the chromepiece and make sure is touching a little copper rectangle/square .
Edwin