Thanks, Ryan. The revised file fixed up my problem, too, in conjunction (of course) with changing the sort parameter in the file to “‘name'” from the default “‘ID'”.
What strikes me as very odd, though, is that the Sidebar template in the default (Kubrick) theme has a place for sort order to be specified where it calls the function list_cats — and the Codex even points one to this line in addressing the issue of Categories sort order. I don’t quite understand why the Sidebar template is overruled by the file in wp-includes, instead of the other way around.
I am just a newb with WP, though.