What happened to my cheesecake?

We had the in-laws over for dinner and I decided to make cheesecake for dessert. Nothing fancy, just a plain 3-step cheesecake in a pre-made graham cracker crust. I've made dozens of them in the past, and they always turn out great. For some reason, something went terribly wrong this time. This is what happened:


So, I made a new one at last minute. Exact same recipe, exact same ingredients. The results were much better this time:


I still have no idea why this cheesecake turned out great while the other one mysteriously flopped. If anyone can tell from these pictures, please let me know.

Cheesecake (from Philadelphia Cream Cheese Cookbook)

2 pkg. (8 oz. each) PHILADELPHIA Cream Cheese, softened
1/2 cup sugar
1/2 tsp. vanilla
2 eggs
1 pre-made graham cracker crust.

Preheat oven to 325°F. Beat cream cheese, sugar and vanilla with electric mixer on medium speed until well blended. Add eggs; mix just until blended.

Pour into crust.

Bake 40 minutes or until center is almost set. Cool. Refrigerate 3 hours or overnight. Store leftover cheesecake in refrigerator.