Smooth Scroll doesn't work for top-level navigation items

[johnnycho]

Here is a sample WordPress site with jQuery Smooth Scroll activated:
http://wpsample3.johnnycho.com/

In the top navigation menu, you'll see two items, called "Scroll Test 1" and "Scroll Test 2." Each of these has one sub-navigation item -- one is called "Scroll Test 1a," the other "Scroll Test 2a."

For some reason, the sub-navigation items (1a and 2a) scroll beautifully but the top-level items (1 and 2) don't scroll at all -- they just go straight to the anchor.

Shouldn't 1 and 2 scroll as well?

Thanks.