I noticed the other day after creating the custom People Results page that the button of "Show more options" was not working and when I clicked it, a yellow exclamation of a Java error showed up at the bottom-left of the IE window. After a lot of headache I was able to figure out the problem.
In my quest for the perfect (for our company) people results page I removed the "People Search Box" that was in there by default at the top, in favor of a custom icon and link back to perform another Advanced People Search. Well that was the problem. Apparently for the "Show more results" link to actually work you need to have that search box there.
I added the People Search Box back in and marked it as hidden and everything started working again