nodes don't sort chronologically

Sitemenu output doesn't appear to sort my nodes chronologically. I've examined the code, and it looks like it intends to sort them descending by date modified, but that's not happening for me. The nodes in question are published (I saw the "status = 1"), so I'm not sure what's causing the problem. I have certain items that I want to appear at the top of the list - in fact, it would be really nice to be able to specify order for nodes under each taxonomy term - and I've changed both the creation date and made a minor change to update the change date, but it still sits at the bottom of the list.