I got a problem with reporting services, running local rdlc files on the 2005 version.
I have in the HTML a report viewer set to run locally as follows :
I had the same problem and in my case it turned out that I have supplied the a dataset that was not the actually the object type that the report expected.
In my situation the report expected a business object, but I have supplied a SQL Data source.
I also encountered this same problem when there was parameters on the report which were not allowed to be null or blank but the parameter values was not supplied.
Also note that in order to set a data source in code it has to be done in the onload event and not in the page_load event.