I don't know why. I recently bought a new video card, and the gameplay runs silky smooth. But as soon as a cutscene starts up such as the opening cutscene or some in-game cutscenes, the framerate will grind to a halt. The framerate does the same thing when I am on the paladin as well. But Far Cry 3 does the same thing to me as well.
I have no idea what is causing it but it sure is annoying.