We have provided a fix in the latest internal build (v126.96.36.199) which represents downloading the report as a PDF file if it is printed in FF19 or a later version. For more details, please check the explanation in the mentioned by Master Jedi forum thread: Unable to perform print operation
I hope this helps.
the Telerik team
Telerik Reporting Q1 2013 available for download with impressive new visualizations. Download today from your account.