Theme Gives exception for report viewer Silverlight

[Ubuntu]

Dear All,
    I try to apply the theme as follows:
    I also referenced the theme dll
    

<Grid x:Name="LayoutRoot" Background="White">
    <my:ReportViewer x:Name="reportviewer" FlowDirection="LeftToRight" telerik:StyleManager.Theme="Summer"
        ReportServerUri="../ReportService.svc"
        Report="ReportsLibrary.EmployeeDepDirectorMgt, ReportsLibrary, Version=6.0.12.330, Culture=neutral, PublicKeyToken=null" />
</Grid>

    But I got the exception when the report loads says "Set property '' threw an exception." ... any help!!

Regards