Forum:KB:How come General Grievous acts like they never met?

In Episode III, General Grievous says to Obi-Wan (and I quote almost perfectly): "You fool! I've been trained in your Jedi arts by Count Dooku." But in Clone Wars, Obi-Wan and the General fight, like, every other episode. Obi-Wan would know that Grievous new how to fight! Is this just a mess up on LucasFilms or am I missing something vital?????