From my experience, the transponders don't tend to be re-programable, so if they have been previously coded to a different car, they will not work.
This is what happend to me, as of the two flip keys I bought of ebay, neither of them would program to my car.
You can check to make sure a key has the correct electronics in it so that it can be matched to the Immobilizer by:
[Select]
[17 - Instruments]
[Meas. Blocks - 08]
Group 022
[Go!]
The value in field 3 must be 1. If value is not 1, the key is not capable of being adapted to Immobilizer.
You can check each key in this manner.
I bought new transponders, cheap enough, from..
http://www.hickleyvaltone.com/diagno...ge=transponder
Mine were the Cypto 48 type..