Symptoms
On a computer that is running Windows Vista, you install a default instance of Microsoft SQL Server 2005 Service Pack 2 or alater version of SQL Server 2005. On the same computer, you install a named instance of Microsoft SQL Server 2008. For example, you install an instance that is named “SQL2008.”
In this scenario, you may receive an error message that resembles the following when you start the SQL Server 2008 Reporting Services Configuration Manager:

No report servers were found. Details: Invalid namespace
Resolution
This problem occurs if the SQL Server 2008 Reporting Services Configuration Manager points to the SQL Server 2005 Reporting Services instance, and it cannot find the SQL Server 2008 instance.