Many people have had this problem since they first came out with the security feature. It will also sometimes happen if you use the remote to lock the doors then use your key to unlock itthis happened to me. Is the little red light on in the lower right corner of the dash? It might have to do with the security chip in your Key. I locked the truck back up, walked away about 50 ft then re approached the vehicle. This time everything worked fine and has been normal ever since. Not sure what causes it but it is a security feature on the newer trucks. If that doesnt work try the second set of keys you got with the truck.