Im a locksmith here in town, and we see this alot. Usually the lock it corroded, because noone uses the key (like myself) just uses the remote to lock/unlock.
Spray alot of WD-40 in the lock, and if you have PB blaster works really well too. and then run the in/out alot, and usually that takes care of it.
If its really corroded, just pull your door panels, and remove the locks, and just get 2 nre onrd, from a locksmith.