I just broke down and bought a new key. At first the door lock/unlock functions started working only intermittently. Then the same happened to the trunk unlock/open. Eventually none of the buttons on the key fob would work. The key would still start the vehicle. I tried reprogramming several times, both ways described on this site with no success. Spoke to a technician while at the dealer parts counter and he claims he has seen keys go bad although couldn't elaborate. Second key is still working fine and the new/repelacement key also works fine with all functions working once it was programmed.

Not sure this is the same problem described above, but it's another data point. Hope it helps. BTW - the key was $165 including tax...most expensive key I have ever purchased. Ordered late Wednesday and picked it up on Friday - apparently they are all cut in NJ. You need to have your license and ownership of the vehicle with you before they will process an order.