Scroll long dropdown menus

I have a drop down menu (in the Full Frame theme) with 17 items on it, but only about 11 show on the page. I'm unable to get it to scroll so I can access the other items. I cannot reduce the number of items (final total will be over 50) but may have to just remove the entire list (assuming I can do this). The top level parent entry points to a page which shows links to the 17+ pages - so I may just solve the problem that way. Any ideas? PS The site URL is www.planetpicture.net Many Thanks, Al