I'm actually having the same problem.
I've been upgrading my site to WordPress 2.5 from ver 2.1.3 and in my old site I have a page listing of all "authors". When you click on one, it brings up the author template whether they've posted anything or not. Using the Role manager plugin, they are allowed to register, change their profile, and post to a wikimap (again a plugin) on the site. In 2.5, it seems that something from the wordpress core is overriding my request for an author page. I've disabled all plugins, switched to the default theme, and it still does it. I call the authors' pages by using this 'http://www.mywebsite.com/?author=10'. I've also tried '/author/bob' with the same results. As long as the author has made a post, the author page will show up using the author template, otherwise it tells me that what I've been searching for can not be found.
Any help on this would be super. I'm totally fine with editing the wordpress core, if that's what is needed. I'm just not sure where to begin and what to look for.