Problem with viewing user account page

Apologies if this is intentional, but install usernode and go to the original user profile at /user/%uid as an anonymous user. It works.

Login and then try again to go to /user/%uid
404 error!

Why is this behaviour different depending on whether you are logged in or not? (It's not permissions, I have triple checked, and anyway that would give a 403, not a 404.)

Also, because the user module still exposes a "View" tab when you edit your account details, there is a link to a page you cannot access. :-(