I'm going to go with the explanation that I first read in C.S. Lewis but which I'm sure didn't originate with him: To speak of God knowing something "before" it happens is meaningless, because God does not perceive things in time. This is not speculation: Time is only a property of this universe; it is a dimension like the three dimensions of space (in this universe). Since I'm assuming that no one will argue that God exists in three space dimensions in our universe, it is reasonable that he does not exist in time, either, especially since it is his own creation. So although we can't conceive of it, God perceives everything in the same timeless eternity, and cannot "predict" anything any more than you can predict something you are watching happen in front of your face.
"We are symbols and inhabit symbols; workmen, work, and tools, words and things, birth and death, all are emblems; but we sympathize with the symbols, and being infatuated with the economical uses of things, we do not know that they are thoughts." - Emerson, "The Poet" (Essays, Second Series)