Fred,
Can you get under the car with a light and see up to where the lock mechanism is? If so, then have someone try to unlock it while you watch. I had a similar thing on a car years ago. Replaced the stick up hood pins with a new locking one and soon one of them wouldn't open. Turned out that I had gotten some dirt down in the lock slot and it was blocking the key from turning more than just a fraction.
Another thing you might look at, is the hood completely flush on that side as it normally is. I doubt if you have anything under it as it locked ok, so that would seem to point to the other problems.
Ron
