Floating Dropdown menus are not fixed (CSS issue)

Using FCKEditor 2.6.4.1 with an external Toolbar which I have fixed in position at the top of my page (inside a DIV container). When I scroll the page, the drop down menus in the toolbar scroll with it, while the rest of the toolbar stays fixed. This effectively makes the drop down lists disappear from view if the page is scrolled down even a little.

This is happening with Safari browser, not IE. Can anyone advise where I might be able to tweak the CSS to keep the dropdown menus fixed with the toolbar? (e.g. Styles, Format, Font, Size)

Thanks.

Geoff