]

] But then he says "You should not have believed me; for virtue cannot so inoculate our old stock (another gardening image!) but we shall relish of it. I loved you not."

] Sometimes I tend to think that negates the earlier declaration. But on the other hand, maybe he's just lashing back at her because she has hurt him? Or maybe this is for the benefit of the eavesdroppers too--Polonius in particular?

I have always felt that Hamlet (a rather shrewd fellow) was aware of Polonius manipulating Ophelia and that his actions in spurning her in this scene were to offer her some protection from her father's machinations. While Hamlet is generally disappointed with women and particularly with his mother, he seems to genuinely care for Ophelia. I also think there is an element of conflict in that he knows he should avoid her because all his focus should be on his vengence, but at the same time he can't keep away. As a result he draws her into his feigned lunacy with his visit to her closet, and again in the scene with the players. Having broken it off with her in the earlier scene, he still gravitates towards her to "lie in her lap". I think he just can't stay away despite his resolve to leave her out of his plans for revenge.