The Caret is not visible when the RadRichTextBox is the only one control hosted in a form. Resolution: This issue is addressed in the new version of the control - RadRichTextEditor. Please use the new control instead the RadRichTextBox.
Has nothing to do with the RadRichTextBox as the only control. It can be together with a lot of other controls and still the caret does not show up until you click on the RadRichTextBox with the mouse.