In Wordpress 2.5.1, after you've created additional publishing users, the administrator account can no longer publish posts or pages. Or rather, the administrator can publish, but it appears under another user's name as the administrator's account is not an option in the drop down.
After quite some digging, I found a solution, or rather a work-around, posted by jmrussell on this Wordpress forum:
- Once the error occurs, go to the Users page in the admin section of the site
- Select the checkbox next to the administrator's name
- In the dropdown above, set "Change role to..." to Administrator and then, with the administrator only selected, click Change.
Now your administrator should be able to publish. You can go back and edit each post that may have accidentally been published under another username by modifying the Post Author field and setting it to your administrator's name.