Chart control -- config error

I added a simple Chart control to my previously working application. Now it still works fine on my local development server, but it generates this error on the discountasp.net hosting server:

--------------
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.
Parser Error Message: Could not load file or assembly 'System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
----------

I tried adding System.Web.DataVisualization.dll to application's App_Bin folder, to the /Bin folder, etc., with no success. I would appreciate any help on how to make this work.

Thanks,
Kumar