Firefox 28 on Windows XP. My usual browser, loaded up with all kinds of extensions and stuff, so I also tried:

Chrome 35.0.1912.2 (from portableapps.com) on Windows XP.

So as to make sure it's not my fault for using XP, I went and updated my Arch Linux box and tried:

Firefox 29.0 on Arch Linux

Chromium 34.0.1847.132 on Arch Linux

Both of those browsers are untouched by extensions.

In every one of these cases, I go to duckduckgo.com or next.duckduckgo.com, go to the settings, change "Auto-load" to 'Off', type the test search "Rob Hubbard" into the search box at the top, press enter, scroll to the bottom of the page by dragging the scrollbar with the mouse, and see the text "More Links..." automatically change to some animated dots and then the further results appear a moment later.

Hope all this detail is helpful!