To reproduce:

1.Create a simple .doc file with a table 2x2.

2.In the last cell insert an image or an email (should be tested with jpeg image as well).

3.Copy the whole table and paste in the RichTextBox >> First Look example in the Demo application

4.Try to save the file in RTF. As a result Unhandled exception occurs.

The same issue occurs when the content is exported to html.

Resolution: 
This issue is addressed in the new version of the control - RadRichTextEditor. Please use the new control instead the RadRichTextBox.