To reproduce: 1. Open ThemeViewer 2. Choose theme Desert 3. Check View RTL support 4. Check 'Aero mode on' of ribbonbar & backstageview, after that click on 'show form' button 5. Check 'Aero mode on' of RibbonBar & Office2007 App Men, after that click on 'show form' button and will see that ThemeViewer crash When set theme Desert and change values of the properties of RibbonBar in the VisualStyleBuilder generate the same error.