You haven't shown any HTML. Is there an href on the button?
You need to call e.preventDefault() or else return false from your click function to prevent the default action on the button. (preventDefault() is preferred).
Are you using jQuery Mobile? (It is included by default in Rhodes projects. If you aren't using it, you would have removed it yourself.)
Be careful about using IDs with jQuery Mobile. They must be unique across all of your pages. (Not just within a current page.) I avoid using IDs completely. Did you use the ID pageDown in two different pages? It sounds like you may have.
Why are you using unbind()? That raises a smell. When I see unbind(), I almost always find that it is a workaround for some "mysterious" problem. Did you have a mysterious problem that unbind() fixed?