After upgrade to 3.5.9 (from 3.0.6) I can’t create new message. After clicking on the New message button I get “You do not have sufficient permissions to access this page.”
I had to upgrade manually – deactivated the plugin, uploaded the files and activated the plugin again, so maybe some other changes (in database) are needed?
This is very strange, nothing has changed on latest version. Did you copied some file in the wp-content/extensions/emails folder to customize the theme? Only themes can be copied there.