Not working...

I'm getting "object doesn't support this property or method" every time when I use the workaround in /grid.howto.fix/sort-empty-cells.html

Any ideas? I've followed the example closely within my solution and get the error when it executes this line:

obj.setDataProperty("value", function(i, j){return formats[j](myData[i][j]);});

(The error actually throws in the grid.js itself...)