When the page is refreshed the information on it, is resend to the server. That is the reason why the row is duplicate. This is a normal browser behaviour. It is not possible to be prevented.
the Telerik team
Register for the Q2 2011 What's New Webinar Week. Mark your calendar for the week starting July 18th and book your seat for a walk through of all the exciting stuff we will ship with the new release!