Problem with richtextbox - copy and paste

I have a RichTextBox that I read of the database access 2003 without problems, also modify the text manually and recorded without problems in my database.
The problem is when I copy plain text from the clipboard into the RichTextBox never recorded in the database.
I am using this code that works fine to record in the database

Dim d = TreeView1.SelectedNode.Tag
Try
con.Open()
com = New OleDbCommand("UPDATE SubCausasDenegacion SET txtAntecedentesHecho = '" & TextBox1.Rtf & "', txtFundamentos = '" & TextBox2.Rtf & "' WHERE idSubcausaDen = " & d, con)
com.ExecuteNonQuery()
con.Close()
Catch ex As Exception
If con.State = ConnectionState.Open Then
con.Close()
End If
End Try

thanks.