Most people who get these problems seem to be on a server that uses a hardened version of PHP.
Unpack and upload it to the /wp-content/plugins/ directory.
Activate the plugin through the 'Plugins' menu in WordPress.
Here are some key features of "AJAX Referer Fix":
· The "You don't have permission to do that" error when performing certain actions, even though you are in fact logged in
· The "Are you sure you want to edit this page: ""?" confirmation when trying to save a post or page
· Inability to remove pages or posts using the Management panels
· And possibly other problems that have similar symptoms
· WordPress 2.0.3 up to 2.3.3