If you replaced the key and/or immobilizer ecu that is attached to the ignition housing then yes, The immobilizer system needs to be programmed. If you bought an un-coded ignition lock cylinder and matched it to your original key and replaced only this lock cylinder into your original housing then no, you should be good.
(Figured I'd combine my comments into an answer for anyone's future reference, since OP's been MIA since '12)
When diagnosing an engine that won't start, it's helpful to remember what all is needed in a working engine: fire. Since a non-starting engine won't have "fire", a good checklist to run through is: