Ah…that should’ve been obvious. Thanks, though.
Nevermind, has nothing to do with Simple Facebook Connect. In a rush, I didn’t read if ( get_the_author_meta( 'description' ) ) : ?>. I didn’t enter a description for the FB user, so I didn’t get the author archive. Simple stuff when you’re paying attention.
Update: this is a live blog, and the link given above no longer has the problem (nextpage tags were removed). I’ll look for something they’ve published in the past to see if I can get another specific URL.