jQuery Grid Plugin - jqGrid

After upgrading to 3.5.3 from 3.4.2 $("#gridName").trigger("reloadGrid") stopped working from the function called on LoadComplete but $("#gridName").trigger("reloadGrid") works from a button on the page once the grid is loaded. 

The grid is loaded via json fed from a url. The server gets the initial request on load but never gets the second reload fired on loadComplete. 

    $("#gridName").jqGrid({

        url: 'WSGridGetJson.aspx',

        datatype: "json", 

        mtype: 'POST', ..........

I've traced the process to grid.base.js line 588

populate = function () {

     if(!ts.grid.hDiv.loading) { ...

It appears that populate will only happen if the grid is not loading and I assume that loadComplete is part of the loading process. This must have been different in version 3.4.2. 

Can I clear the loading flag from on loadComplete process. If so, how and what might be the reprecussions of such a change is standard process? Can PostData be set before the grid is created in verison 3.5.3. ( I believe this method of shaping grid data was devised back in version 3.1, perhaps the process has changed since then)

The grid is reloaded on loadComplete to set PostData to variables acquired after the page containing the grid is created to control the loaded data set. 

Called from on loadComplete function.

        $("#gridName").setPostData({ un: "x", ci: "y", pll: "z" });

        $("#gridName").trigger("reloadGrid");