Grid - Clicking on the Header Line to Sort

Think I founf the issue (searching on here, not Google) Few links ..

http://www.telerik.com/forums/unable-to-cast-object-of-type-telerik-web-ui-radgrid-to-type-telerik-web-ui-gridtableview

leads to

http://www.telerik.com/forums/255649-unable-to-cast-object-of-type-telerik-web-ui-radgrid-to-type-telerik-web-ui-gridtableview

and then

http://weblogs.asp.net/scottgu/gotcha-don-t-use-xhtmlconformance-mode-legacy-with-asp-net-ajax

Which we have, need to remove this in the Web.Config :-

    <xhtmlConformance mode="Legacy"/>