wijgrid: Cannot call method 'subscribe' of undefined

I implemented 3 out of 4 grids in the very same way.
But when I add 4th grid, the error came out:
Uncaught TypeError: Cannot call method 'subscribe’ of undefined
The code to generate the grid is as below:

 $("#LocationGrid").wijgrid({
            allowPaging: false,
            allowSorting: true,
            data: data
        });

Please help!
Thanks in advanced.