this.radRichTextEditor1.Text = null;
Thank you for reporting this. Currently, the possible solution that I can suggest is to set the Text property to string.Empty:
this.radRichTextEditor1.Text = string.Empty;
I hope this helps.
Dess | Tech Support Engineer, Principal
Love the Telerik and Kendo UI products and believe more people should try them? Invite a fellow developer to become a Progress customer and each of you can get a $50 Amazon gift voucher.