Need to enable Web.DataVisualization?

I need to generate some reports with charts.  On all my machines (including a DC) with .NET 4 except one, I could simply load the DataVisualization assembly with:

[System.Reflection.Assembly]::LoadWithPartialName("System.Web.DataVisualization")

On one Windows Server 2008 R2, the above statement returns $null.  Is there anything I need to do to enable this particular assembly?

Thanks.