Hi Guys, I have a similar issue, if not the same.
Unplugged the Battery, then disconnected the screen connectors carefully with a plastic spludger.. and connected the bare new screen to see if it worked before doing the repair, Nothing.. no back-light or any signs of life, so reconnected the old screen with the same issue :(
iTunes does recognize the phone when its plugged in, but my PC is not authorized for this phone.. when the phone is on charge it draws power, but just pings every 5 seconds.. All connectors are clean with good connection, there were no screws in the connector plate after removing them, and the phone was working fine prior to removing them..
Sorry this is not a solution Miki.. would have loved to read one here.. :(