Why is my display screen white out?

I need some help here. I encounter a few problem while repairing my iPhone 3G. Recently I replace a new orange ribbon cable because my power button not working. At the same time I change to a new back casing I bought from the internet. The installation went smoothly until when I switch it on, there is not signal connection. After going through your repair manual. I relised one side of the orange ribbon cable was not screw on (the one just below the cable '6'). I re-install everything again. This time, when I switch on the phone. The apple logo stay on longer than usual. Then my phone lock appear. But my touch screen not working. I open up the phone again to check on all connectors, install again. Now when I press on the power button. It show I need to connect for power (like low-batt). I tried charging it for 1 hour. The phone able to switch on, apple logo appear, but the display screen turn white. No sound, No vibration, No respond when connect to power. Tried hard shut down but the display screen remain white. Have to leave it till battery flat. Any advise what went wrong here? Is the display screen faulty?