Google Webmaster Tools is showing some pairs of pages with "duplicate titles". Problem is one of each pair is an old page which no longer shows in "All Pages" in the WP dashboard. I used the "Redirection" plugin to redirect from the old page to a new one with a different path - but with the same page file name and title, thus the Duplicate Title errors.
Now I want to delete the old invisible (in the dashboard) pages. I'm not comfortable messing around in the MySQL database tables.
How can pages not show in the Dashboard? Maybe Google is fooled by an old "sitemap.xml" file? I just uploaded a new one, but it probably hasn't been crawled yet.
Any other ideas? Any plugins to clean up problems like this?