We test the shiny new 2.5.1.
Everything's kinda borked, let's see if we can figure out why.
Edit, 3:25pm: My slightly unconventional use of The Loop came back to bite me in the ass.
It turns out that I should have been using query_posts() before my call to have_posts() all along, and upgrading from 2.5 to 2.5.1 finally prevented me from getting away with it.
On the upside, though, figuring out the extra parameters for query_posts() means I have finally, /finally/ nailed the goddamn "Why does WordPress make it so fucking difficult to show the [n] most recent posts in category [x]?" issue.
The solution?
query_posts('category_name=fnord&showposts=10');
Praise Cthulhu. WordPress is getting closer to useful by the day.