I have this Error after upgrade in 2013.1.403.40 of RadRichTextBoxRibbonUI:
Method not found: 'Telerik.Windows.Documents.Model.Styles.StylePropertyBase Telerik.Windows.Documents.Model.DocumentElement.GetPropertyDefinition(System.String)
We are glad to hear that you resolved the issue yourself. Do not hesitate to write back if you encounter further issues.
Kind regards,
Boryana the Telerik team