OH, what a relief!!! had the same problem with black LCD after replacing the digitizer/screen and WiFi antenna. I was soooo careful throughout the procedure, even wearing my ESD wrist strap while handling. Resetting the LCD connector three times did not help. BUT, the 15-20 Second hard reset (Power and Home Button) did the trick!
This might be a good note to add to the rpair guides... sounds like a common enough issue.
Thanks everyone!
CT