Check again the digitizer cable. Take it out and use "contact spray" on the contact. I always use contact spray on these kind of contacts. Typically inserting the display cable in unibody MacBook Pros I find often the backlight does not work. I take out the cable, use a little contact spray on the contact and cable and insert it and it always works. Make sure the little retaining flaps are pushed down. A good investment is contact spray, technical alcohol and a air spray can. They always come in handy.