How to duplicate an existing SSRS report in AX 2012

I would like to create a copy of one of the existing SSRS reports in AX 2012 to use as basis for a customized report.

I've tried 

1 - Open VS

2 - go into the application Explorer

3- choose the report you want duplicate

4- duplicate the report

5- for to each data set parameter  change the name of the report to match the new name

but in the VS when I try to Edit the report design its throwing the error

"Object reference not set to an instance of an object".

Plz help me on this.

Thanks