For security reasons DTD is prohibited in this XML

I am getting this error while running a very large dataset. Please help..

The full description of the error is : "For security reasons DTD is prohibited in this XML document. To enable DTD processing set the ProhibitDtd property on XmlReaderSettings to false and pass the settings into XmlReader.Create method."

I am having hard time figuring out a solution for this. I am using sql 05, SSRS 05, Report viewer

And this problem is popping up only for larger datasets, (works fine for smaller ones)

Thanks
Satya