Footer on Single Post Pages > some of it is missing

I've placed the following code in the area for "Footer: Single Post Pages":

%wp-print% | %wp-email%| %sociable% | <strong> Categories:</strong> %categories-linked(' , ')% |<br /> %comments('0 comments yet, your thoughts are welcome!', '1 comment so far, be the next!', '% comments - be the next!', 'Sorry, comments now closed')%

But the "comments" section is not showing up on those pages at all, just the part up to the "categories". Any idea what's going on here and how to fix it?

http://lindafarmer.com/2009/04/twitt...following.html

Thanks!!