The scrollbar position normally won't change as the user navigates between states (assuming it's really the same scrollbar, shared across those states). I don't know of any way in Catalyst to force the scroll position to reset when you visit a certain state, but this is easy to do with a snippet of code when you're ready to take the project into Flash Builder.
For a list, just add this code to reset the scroll to the top:
For a scroll panel, use this:
scrollPanelId.contentGroup.verticalScrollPosition = 0;
In both cases, if the tag representing the list/scrollpanel doesn't have an id="..." attribute, you'll need to add one so you can refer to it in your code.