It is possible to run CR in a pure 64 bit Environment

My development workstation is Windows 8.1 (64bit) and I am using Visual Studio 2013.5.

I started a new WinForms project.

I changed my environment to x64 from Any CPU.

I created my dataset and a CR report.

I added the following to my App.Config:

<startup useLegacyV2RuntimeActivationPolicy="true">

          <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0" />

</startup>

I added a Report Viewer to Form1 and Loaded my report in the Form Load Event and set the DataSource just as I always do.

If I run it now my app crashes.

I have both the CR Redistributeable 32 and 64 installed.

If I just change the CPU back to Any CPU it runs fine.

What have I done wrong?