The experienced error is due to a compatibility issue between Telerik Reporting and Telerik RadControls for WPF. We have already provided a fix available in the latest internal build v126.96.36.199 of our reporting product.
Give it a try and let us know if you have any further questions.
the Telerik team
Telerik Reporting Q1 2013 available for download with impressive new visualizations. Download today from your account.