drop-down menu does not work

The first run of this theme was not intended to use the dropdown menus. In the base theme, I'm phasing out the dropdown menus because of too many issues maintaining them, and making them work for all cases. the Fusion theme has already removed ALL support for menus, requiring you to either place the default drupal menu blocks or use a contrib module.

I'd recommend looking for a contrib module for the dropdowns (I know there are a couple for D7 ready) and then working with CSS to style them to your needs.

I may look at including some CSS for things like nice_menus (and I forget the other ones name) that would let someone pop in the module's dropdown menu block(s) and have them at least look like the rest of the theme. But that is probably a ways off unless someone spearheads a patch for that.