This may sound stupid, or might not be close the the answer you are looking for, but have you checked to make sure the battery terminals are clean/tight? I had a similar problem a few months ago, and it was hit and miss starting. Since it was cold, I assumed it was happening because of the weather. I had the battery tested, and it was fine. Dealer checked it, and it was fine. I cleaned(using wire battery brush and sand paper) the terminals and all related wires/rings, and no problem since. Like I said, don't know if that's your problem, but it's worth a shot.
