BC Boutique template Dropdown children menu issue

I am building an e-commerce site based on the Boutique template. So far I have been able to adapt most elements but am struggling to get drop down menus to work we way we want. The problem we are experiencing is with child element of the main navigation. Things work fine with the first level of drop down, but following levels are not hidden, only becoming visible on rollover. Can anyone help me solve this problem please.

The site can be viewed at:

http://pharmahp.businesscatalyst.com/about-us.html