Remove CuteEditor from the page and add the following code instead:
<asp:Button id="btnUpdate" Runat="server" Text="Submit"></asp:Button><br/>
<asp:textbox id="textbox1" runat="server" TextMode="MultiLine" Height="250px" Width="730px" Font-Name="Arial"></asp:TextBox>
Then test again.
asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx