Sat down in front of the machine last night and stared at Emacs, trying to remember what the crap I'd been working on 5 days earlier. Eventually remembered it was that kdict thing.
Stared at the code, then gave up on that and started playing with it for inspiration. Immediately stumbled on a bug in the multiple-selection checkboxes when there's only one set of them (that is, the search word is disambiguous as to search category): the opening FORM tag was missing. Fixed it. Went to bed.