I'm afraid this is the first I've heard of a "writeback" flavoured Blosxom. Try dropping the "/+writeback" bit from the end of the URL.
Now that we're on the latest Blosxom, we can try out some of the cool plugins people are writing for it. One is AutoTrack, an automatic TrackBack plugin that follows links in your stories and auto-pings those links if proper TrackBack information can be found. That's what I'm playing with now. If all goes well, a reference to this story should show up on that site.