Pages, navigation and drop down menu’s

All

Having some problems with my page navigation. I should have a drop down menu with sub headings (parent & child headings) but these do not appear.

http://www.belttightener.com

When scrolling over business profiles a drop down list should appear with some company names but this doesnt seem to work.
It did however seem to show on a mac I was using?

the pages are there as you can go directly to them, see:
http://www.belttightener.com/business-profiles/system-solutions-inc/

Help would be much appreciated

Thanks
Simon