After making a selection in the control and changing the theme two times in a row an InvalidOperationException is thrown about the animation.
Declined: The issue is caused by combination of the current implementation of the Telerik AnimationManager and limitations/behaviors of the Silverlight framework. In order to workaround this issue all that is requried is for the AnimationManager to be disable. The next code snippet shows how to disable it in the XAML of your application: xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation" ... <telerik:RadComboBox telerik:AnimationManager.IsAnimationEnabled="False" /> ...