After I upgraded to 0.8 the users can not update their profiles if they are not administrators. They get an "An author slug cannot be blank" error when trying to edit/save their profile. And they do have an author slug. I had to downgrade to 0.7 to make it work again. These users don't have (and should never have) access to modify the slugs themselves.
And also: I posted this in the contact form of your site. It was very questionable if the form went through or not. The message after posting was very unclear.