QTH.COM Swap Chat

I would like to search ads in a particular category (RADIOHF, BOOKMAG, etc.), using Advanced Search, but it's not working for me. If I select a single category from the Restrict Category dropdown list, and fill in nothing else in the search form, I get the same results every time, regardless of what I choose. The list looks like all the ads, most recent first.

Am I doing something wrong to search by category? Putting a category name in the "any of the words" box doesn't work: it just returns ads with that category name in the body of the ad.

Thanks,
Dan, KB1RT