Thanks for the link, it looks like your flash is causing some interference here. If you get rid of the gap it should allow you to scroll down the product and support menus.
To do so you will need to edit the CSSMW > cssmw_home > menu.css file. In here look for the following style:
Remove the padding-top value from in here and it will bring the sub menus up to main nav. This should prevent the menu from collapsing on you, let us know how this works.