This issue pertains to CRM 2011 using ADFS on a Windows 2008 server.
After resolving some issues with having multiple bindings to the CRM website, I am now faced with the problem that after a certain interval, the user receives a 404 - File or Directory not found page when trying to access the CRM page. It's not until the user closes all browser windows and re-opens Internet Explorer that they are able to access the page again until the next time the page errors out.