I am frequently getting an error message similar to the one below when previewing a report in the Visual Studio 2015 Community Edition with SQL Server Data Tools (currently using 14.0.60629.0 though error has occurred in all versions).
[rsInvalidReportDefinition] The definition of this report is not valid or supported by this version of Reporting Services. The report definition may have been created with a later version of Reporting Services, or contain content that is not well-formed or not valid based on Reporting Services schemas. Details: Data at the root level is invalid. Line 53, position 374.
Once I receive this error message if I go back to design mode and hit preview again the report will display.
I am targeting SQL Server 2012 and this error occurs for existing reports and new reports.