Something was wrong with the categories on this page. They just wouldn't produce a list of entries any more. I updated Wordpress to the latest version, and everything works again.
Unfortunately, there is a bug which causes entries with 0 values in the URL's to fail - at least in my situation. I've fixed it twice already but it keeps making comebacks every time I update. They seem to be holding on to that bugfix for version 2.3 and no sooner.
Thankfully, I can just go in there once more and fix the damn thing myself. I imagine that it would be infinitively more frustrating than having to fix it, to just have to live with it and wait until they release a fix.
Of course, this requires some programming skills, or at least the ability to read, and/or apply a patch. It's not that hard, really.