Hyper-correction or hyper-urbanization is the term for the practice of misusing a nominative or reflexive pronoun when an objective one is called for. The hyper-correction version is a referrence to the idea that is an overreaction to a construction of the sort: me and him went fishing last weekend. If I were to say something like just between you and me and you were to huffily say that I should have said just between you and I, I could reasonably say that you had hyper-corrected me.