Theli

I wouldn't call this "knowing", but rather predicting. Omniscience doesn't say anything about predictions. It means knowing the future actions.
Let's state this mathematical example.
2*X=?
Where X is an increasing number from 1 to eternity. If god would be omniscient it would imply that he knew the answer to every 2*X. His answer could not come out of calculating the answer, because that would mean that he didn't know the answer prior to calculating it.
He would need infinite knowledge, and such a thing brings huge problems.