Hi Craig,
You may need to first reference the chart dlls from bin property. To check if this is causing the problem follow these steps:
1. Reference the Nevron.System.dll, Nevron.Presentation.dll, Nevron.GraphicsGL.dll, Nevron.UI,WebForms.Controls.dll, Nevron.ThinWeb.dll, Nevron.Chart.dll, Nevron.Chart.ThinWeb.dll and Nevron.Chart.WebForms.dll.
2. Modify the Copy Local property of those references to true.
3. Rebuild the application.
4. Try to drop the control again.
Hope this helps - let us know if you meet any problems or have any questions.
Best Regards,
Nevron Support Team