When RenderMode is set to LightWeight and ToolbarMode is RibbonBar, a JavaScript error is thrown.
The errors are resolved and the fix will be available in Q1 2015.
This is not a supported scenario until the RadRibbonBar control obtains lightweight rendering. http://demos.telerik.com/aspnet-ajax/editor/examples/rendermodes/defaultcs.aspx http://www.telerik.com/help/aspnet-ajax/editor-render-modes.html