Sorry to bump an old thread, but I have the exact same problem. Maybe you can recreate this.
I have Google Chrome windowed from the top all the way to the dock. When I access the Launchpad directly from the top (from the chrome window to the launchpad, without going to the side) and then click launchpad, the launchpad cursor is still the "resize window up-arrow" instead of the normal cursor.
Anyone? Bug?