asp.net - Error in Window-Control -

hi have problem window-control, if set browserdialogbox property true im becoming error rendering control - window1: "an unhandled exception has occurred object reference not set instance of object."

synfusion:

        <syncfusion:window id="window1" runat="server" height="200px" width="250px"              title="Öffnen" iconimageurl="~/images/kbd-favicon.ico" enablexhtml="false" browserdialogbox="true" enabletheming="true">         </syncfusion:window> 

i have used syncfusion window control code, working without error have reported. post more of code , we'll see done wrong.

<p>     can find <a href="http://go.microsoft.com/fwlink/?linkid=152368&amp;clcid=0x409"         title="msdn asp.net docs">documentation on asp.net @ msdn</a>.     <asp:scriptmanager id="scriptmanager1" runat="server">     </asp:scriptmanager>     <asp:panel id="panel1" runat="server">         <syncfusion:window id="window1" runat="server" height="200px" width="250px" title="Öffnen"             iconimageurl="~/images/kbd-favicon.ico" enablexhtml="false" initiallyshown="true"             browserdialogbox="true" enabletheming="true">         </syncfusion:window>     </asp:panel> </p>