DEMOI have this 95% complete.
If you inspect the .grid ul after each click on a menu item, the ul's get spit out and jscrollpane decides to re-initialize itself, disregarding the container content.
Jscrollpane seems to be the easiest to implement but this last bit is causing me all sorts of pain. Let me know if there is anything i am missing.
I found this site but i am not sure how to implement the code suggested.
I am so close. Here is the url to inspect and diagnose.
Here is a fiddle
Here