The report definition is not valid. Details: The report definition has an invalid target namespace 'http://schemas.microsoft.com/sqlserver/reporting/2008/01/reportdefinition' which cannot be upgraded.

You may get the above error when trying to view a RDLC report using with the VS 2005 or VS 2008 viewer controls with 2008 schema.

When using local mode, you are using the same report processing engine that was shipped with SQL Server 2005. This engine does not understand the new report definition schema and attempting to load a report created with one of the new SQL Server 2008 authoring tools will result in this error.

Open the RDLC in VS2010 and use the v10 of the report viewer control to run the report.