I finally updated my blog to WordPress 2.1 and Zempt works just swell. I thought I might have more problems than I actually have had. One thing about the 2.1 out of the box, though, is that WordPress returns invalid XMLRPC response to edit an existing entry. The problem was that WordPress was returning the categoryId as an <int> instead of a <string> as the XMLRPC spec says. This would make Zempt crash. Fortunately, someone committed a patch to the WordPress Trac which fixes it perfectly.