Hi,
The reason you are seeing the changes after signing in is because WP Super Cache does not show any cached content to signed in users.
I'm not sure why they haven't cleared them selves out, what you could do is drop by the settings page (/wp-admin/options-general.php?page=wpsupercache) and use the Delete Cache button there, that should rebuild the cache the next time a visitor comes by your site, and thus updating the content for everyone.