Topic moved while posting a forum topic via blogAPI and via rules

Hello, I had some trouble when I tried to use off-line blog editors to post new topic on my Drupal forum. I tried scribefire and zoundry Raven as client editors, and enabled blog API module on my Drupal site and configured the "Forum topic" as blog type. Both of the clients could connect to the Drupal site without any problem. (They explicitly support Drupal blog API.) When I posted an article to the forum, the title of the new post appeared under the specified forum (path/forum/3). However, there was a sentence following the title - "This topic has been moved." and it linked to the container of the specified forum, which is forum/0. The categories showed in the client editors were correct. Each forum was recognized as "container/forum". I didn't know why the post was moved to the root container and left a "shadow copy" automatically. It seems not a problem of the editor but the blog APIs. I'm using Drupal v5.3 now. Can anybody please give some hints? Is there somebody using off-line blogging tools to post forum topics? (I can post normal story without problem, since there has no category being specified. And I have to say scribefire is a very convenient tool to work with Drupal blog API. I also wonder if this would be solved automatically if I update to 6.x. ) Any reply would be very appreciated!