Displaying CLOB data in Microsoft Report Builder reports
To work around this error, you need to set the property DiscourageGrouping to "false" on the clob type in the model. When you redeploy, you'll be able to see the clob data in the report. A full explanation can be found here:
http://blogs.msdn.com/bobmeyers/archive/2006/12/20/getting-grouping-right-in-report-builder.aspx