To reproduce: 1. Install Telerik UI for WinForms Q3 2015 SP1 or Q1 2016 trial version 2. Open Demo Application and navigate to RichTextEditor examples 3. Click on tile First Look and you will see the exception Workaround: Open the solution RichTextEditor from folder Examples. The location where can be found is: C:\Program Files\Telerik\UI for WinForms [Version]\Examples\RichTextEditor