When you try to log into SSRS\'s root site at http:// (servername)/Reports it displays:
User \'\' does not have required permissions. Verify that sufficient permissi
I ran into the same issue myself but with Windows 7 and SQL Server 2008. I resolved the issue following the instructions from Suresh Kumar's blog post at http://skamie.wordpress.com/2010/06/24/ssrs-and-uac/
In a nutshell here are the steps you need to take to resolve this issue:
Start your browser using 'run as Administrator'.
Navigate to the report manager and under Site Settings -> Security assign your account or the local administrators group to the System Administration role.
Then navigate to the home folder and under the security settings assign your account or the local administrators group to the Browser, Conent Manager, My Reports, Publisher and Report Builder roles.
Now you should be able to run your browser as normal and access SSRS without any issues.