I am echoing all of the previous comments. Trackpad and keyboard stopped responding, external mouse and keyboard work fine. Ordered a new cable and swapped for the old one. Took 10 minutes total. The hardest part was bending the replacement cable in a similar fashion to the OEM cable so that it would fit. Tip: get both connectors in place, then press the adhesive down to the battery in the middle of the cable and work your way out to the connectors. The cable will bend accordingly.
My problem was that dust/grit gets into the computer over the years and the cable is sandwiched between the outer case and the battery. Any flex in the outer case will crush the grit into the cable and cause dimples, eventually breaking one of the lines in the cable. See picture.
[image|2132275]
Thanks to ifixit for getting me going again!