I've posted some information in my Blogging category about what I believe is another bug in Radio's trackback.
The nature of the bug is this: If a post is published with links that Radio will send a trackback ping to, but the post is not published to the home page, the trackback pings silently fail. In the post's outbound trackback url data in weblogData.root, an error message of this type is recorded:
Can't create item "radiocommentsManilaWebsite.#newsSite.radioHosting.trackback.users. 0127252.114.trackback.inbound.urls." because "" is an illegal name.
Possible workaround: When first publishing a post, publish the post to the home page as well as any categories that you want to route a post to. After Radio has published the post and pinged the appropriate trackback urls, edit the post to remove it from the home page and re-publish. (This workaround is untested.)
(Hat tip to Lisa at distant, early morning for her assistance in the discovery of this bug.)
Update 04-Sep-2003: Based on what I determined to be cause of this error, the workaround I describe above will not work. If the "Home Page" (main weblog) is checked along with a category, the outbound trackback will display a link to the "Home Page" post. When the post is removed from the "Home Page" and re-published, the previously sent trackback link to the "Home Page" post is then broken because that post is no longer present on the "Home Page".