URLs and multiple blogs

We have 3 users, each with their own blog. Everything is fine when viewing individual blog posts, but the pages that list multiple posts are not behaving as I would expect.

For example, the URL:

mysite.com/.../username

Displays posts for all users, rather than just the user's posts.

I would expect /blog being appended with /username to filter out posts not by that username.

Any ideas/suggestions?!

Thanks,

Ian

A quick follow up; this is weirder than I thought.

If I use the URL:

http://mysite.com/blog/ian

Posts are NOT filtered to just mine.

If I use the URL:

http://mysite.com/blog/philip

Posts ARE filtered to just Philip's.

My head hurts! :)

Ian

Never mind, I've answered this myself. 

The blog URLs are filtering not by the name of the blog, but by the Sitefinity login name of the user. This is less helpful, in particular as some of us have made poor choices of usernames.