pages displaying old versions of themselves, failing to update

a site i have been building was working fine, then i logged in and changed some text on one of the pages – nothing else. nothing in the css, nothing even manually within the html, and suddenly several of the pages began displaying the first version of them that i created. the pages have subsequently been updated (and were displaying properly) – they all appear fine in the wp-admin view, but when they get updated now, nothing happens, and preview page displays only the outdated version of the page. i have disabled all plugins and have automatically (and manually as well) reinstalled the newest version of wordpress. i have cleared the browser cache (and checked on more than one computer) but the issue persists. any suggestions would be greatly appreciated. THANK YOU!