Runtime error when project output type is Class Library

[Mark]

Telerik: 2012.2.912.40 (RadControls for WPF Q2 2012 SP2)
OS: Windows 7

Problem: I have a WPF Class Library project, after dragging a DataPager to my UserControl, I get "Could not load file or assembly 'Telerik.Windows.Controls.Data, PublicKeyToken=5803cfa389c90ce7' or one of its dependencies. The system cannot find the file specified."

But if I make my project's output type to Windows Application, my project runs fine.

Is there an issue with DataPager and wpf class library projects?

Please help.

Thanks,
Mark