I just received a report that many subscribers are receiving an error message on a fresh installation of the latest WordPress release (18.104.22.168)
It seems the header file checks to see if the All in One SEO pack is installed to insert the correct title into the page. The problem occurs when a blog is running without any plugins.
The fix? If you don’t have any plugins running and are experiencing this problem, just update to the patched version. If you are not running into any problems, there is no need to take any action.