Net 4.0 websites running on a Windows Server 2008 R2 server using IIS 7.0. The websites allows Single Sign on via an encrypted token passed in a query string e.g. www.mywebsite.com?token=1159CE30A4ED1148E86D779AC7A1CF4DC75CCEC7213401D13CA181A2ED1C29A8. However, after installing Service Pack 1; SSO has stopped working and the website redirects to www.mywebsite.com. The redirect occurs before any code is hit. No idea what is causing this and any ideas would be much appreciated.