An error has occurred during report processing.
 Query execution failed for data set ‘dataset_0′.
  For more information about this error navigate to the report server on the local server machine, or enable remote errors

In order to see a better description of the error you can either RDP onto the server and run the report or…  

To enable remote errors in Reporting Services 2005 or 2008 run this statement in SQL Server Management Studio: 

Use ReportServer;
update ConfigurationInfo set Value = ‘True’ where Name = ‘EnableRemoteErrors’;

You then need to reset IIS

There are more options here: http://technet.microsoft.com/en-us/library/aa337165(SQL.90).aspx

And here: http://technet.microsoft.com/en-us/library/aa337165.aspx

So now if you re-run the report you can see it’s a data source error – a field name has been changed in the database:

An error has occurred during report processing.
 Query execution failed for data set ‘dataset_0′.
  Invalid column name ‘myNewField2′.