This issue came about as a result of: http://drupal.org/node/233301
A lot of good work was done in D6 to make it possible to use blogapi.module with different node types. However there's still a couple of places where blog module is hard coded.
blogapi_blogger_get_users_blogs() and blogapi_blogger_get_user_info()
These are callbacks for the xmlrpc interface - so we need something there, and it's currently inaccurate to point to the user's blog if they're using blogapi to post completely different content types. There's also no check to see if the user actually has a blog, so it's providing page not found in both cases potentially.