Have you checked the cable that goes down to the motherboard?.
I opened up my 1200 and "accidentaly" touched that cable. Nooo keyboard working and felt quite stupid about it since i recently bought it. Checked the cable and it was actually out of position in the socket. repositioned it but didn't work. I cleansed the cable for oxidizing on the contact surface and got it to work again.
Maybe that's worth checking?