jQuery Grid Plugin - jqGrid

Env: jqGrid 3.7.1, jquery-1.4.2, jquery-ui-1.8.2

Using cellEdit functionality. Whenever I click on a cell it becomes an editable text input field. However when I have Firebug open I see the javascript error "b.unformat is not a function".

I think it is getting called from grid.celledit.js line 63:

tmp =  $.unformat(cc,{rowId: $t.rows[iRow].id, colModel:$t.p.colModel[iCol]},iCol);

The unformat function is defined in jquery.fmatter.js which I also have included within the overall jquery.jqGrid.min.js file.

I suspected this was because of some namespace issue. So I included the script at the top:

jQuery.jgrid.no_legacy_api = true;

This did not help. Any ideas?

EDIT: To clarify this does not seem to affect functionality as far as I can tell now. But it may be in a way I haven't seen yet.