DataGrid OnItemCommand and OnSort command not firing

I have an DataGrid with AutoGenerateColumns False and two
controls defined for OnSort a third column contains a
ButtonColum to add items to a basket.None of the relevant
eventhandlers fire. I have checked the source of the page
and there is javascript enabling the Postback, a Postback
does occur and the Page_Load event fires but none of the
subsequent DataGrid events? What's next in terms of
debugging etc to find out why the events aren't being
fired?