Update 2014-12-03: I have a new, better, simpler fix for this. Earlier this year the original solution I had stopped working. The problem is the electrical contacts (little circular pads for each button on the inside of the fob) were slowly disintegrating. You can tell because the black part is starting to wear through. While googling for fob fixes I discovered some companies were selling plastic inserts with circular metal electrical plates that bridge the original pads. They work because they distribute the electrical charge more evenly and more widely across each electrical pad thus resulting in a better connection. I took a hint from this and simply super-glued little circular pieces of common, household aluminum foil to the electrical contacts. It worked! It worked like it was brand new! I was so impressed it worked that well. That was a few months ago and it’s still going strong so I hope this helps someone!
Fixing your car key fobs with a knife, scissors, elastic, paper and super glue!
So, my car key fob buttons have been deteriorating progressively ever since I got my car four years ago. So, I used a knife to pry open the fob by the seam along the edges. I used super glue around the metal edges of the battery holder, “clamping” metal connections down using an elastic, and, when that was all dry, cut some paper to the size of the fob, put it behind the battery to add additional pressure on the connections, and closed the fob back up. Voila! Fob repaired!