Under the "News" menu, we're using custom links to category archives as well as to individual pages. This means the default Left Sidebar menu for stuff in that section doesn't auto-populate with the same links (or at all). So I've made a custom menu and widgetized it into a custom Left Sidebar that's assigned to everything that fits into that section of the site.
My menu shows up on individual posts and pages, but not on the archives (category, date, etc.) to which the custom sidebar is assigned. I don't see anything obviously different about how the left sidebar is called in the archive.php template. What could be the cause?