WordPress MU 2.8.5.1 released yesterday had a minor bug that prevented a user from publishing or saving a new post. When a user tried to save or publish, they would get an error message saying “You cannot make this user the post author”. The post was still saved as a draft and it could then be published or saved as a draft again without any errors. This bug was fixed in WordPress MU 2.8.5.2 which can be downloaded here.