Anyone familiar with flexcroll? Div hidden overflow problem

sample page is up at http://darrenlasso.com/freelance/frame1.html

Trying to make a lookbook- there is a side nav with div overflow and some java to give it a specialized scrollbar. I’ve gotten it working before, but only when each image on the left nav is defined within a simple <p> tag and not its own div. Once i put everything in its own div (#nav1, #nav2, etc etc) the scrollbar no longer functions- turns into a solid black bar with no scroller. There must be some css definition i am missing on my nav divs. Any ideas?
The css file is at http://darrenlasso.com/freelance/lookbook_web/styles.css (i know its unorganized- still working through it) but the main definitions to pay attention to are the nav1,2,3,4 etc and the ‘links’ div that they all sit within