I have exactly the same problem. When I catch the rendered event and try to call igGridUpdating(X), I'm always getting "cannot call methods on igGridFiltering prior to initialization; attempted to call method X"

Example:

rendered: function(evt, ui) {
                var editing = grid.igGridUpdating("isEditing");
},

When I place a breakpoint at "var editing", I'm hitting the breakpoint and I'm always getting "Uncaught Error: cannot call methods on igGridUpdating prior to initialization; attempted to call method 'isEditing'"

dataSource is JSON data and showing properly in the grid. I can perfectly edit, delete, save,… But every call on igGridUpdating is failing.