The Open Manhole

Why is there a contradiction between saying on the one hand that Man has free will and on the other hand that God knows all future events? Everyone already believes that both statements can be true at the same time--they form the basis for all low comedy. In the movies, we know exactly what will happen when the sloppy drunk meets the heiress in the elegant gown, and we groan at the inevitable when we see the house painter with a full can of paint perched above the sunbather. Like God, we do not cause these events while watching them. Yet it's no use screaming about the open manhole cover. It must be very tiresome to be Him sometimes.