If you install Reporting Services on Windows Server 2008 (RTM or R2) and attempt to verify the installation by opening the http://SERVER/ReportServer site, you may well see the following message:
Reporting Services Error -------------------------------------------------------------------------------- The permissions granted to user ‘MCGEOWN\Sam.McGeown’ are insufficient for performing this operation. (rsAccessDenied) Get Online Help
SQL Server Reporting Services
Additionally, you may be able to access the http://SERVER/Reports site, but will have no permissions:
You may also spend a good while checking DB permissions, IIS configurations, file permissions and so on.