Visual Studio 2010 and Report Builder 3.0 RDL reports use a new schema that is not supported by SQL Server 2008 Reporting Services. They are designed to work only with SSRS 2008 R2. Currently there is no way to publish a VS2010 Report on SQL Server 2008 without some modifications to the RDL code.
In order to publish the RDL in SSRS 2008, the following steps have to be performed:
1. Open the RDL file (not project) with Visual Studio or an Xml Editor.
2. Replace the report namespace occurrences from 2010 to 2008:
Should be replaced with:
3. Report the following Xml Tags (Keep the Xml between the Tags)
4. Save the Xml file and publish the report. This should now work with SSRS 2008.