Author Avatar List Plugin problem

I have a WP 3.0 MU site with multiple authors in each blog. I have the author avatars in a sidebar. I have been using the the Author Avatars List plugin by Pbearne Bforchhammer (WPMU Dev doesn't have a plugin that allows selection of the level of user avatars to display). It has been working fine until yesterday when I added another author. Now it doesn't work at the Main blog but still works on all the sub-blogs, even displaying the new author avatar. On the main blog its says: "no users found." The plugin says it is 3.0 compatible, although I don't if is MU compatible - but it has been working fine for months on my site. (I use it conjunction with Add Local Avatar plugin to upload local avatars and About the Author plugin to display short bios in posts). Any ideas/solutions?