Author archive not working

I have a seemingly simple problem that’s been making me tear my hair out: There are two authors on my blog, myself and a co-blogger. We have the same exact permissions. There’s an admin account that doesn’t post, then two other accounts that do: “Matt” (me) and “Brandon” (him). But check out the difference between:

http://www.ffgeekblog.com/author/brandon

and

http://www.ffgeekblog.com/author/matt

What in the #@$% is going on here?