How can I preserve the search filters in jqGrid on page reload?

I found many discussions that were close to what I need, and this question is the closest - How can I set postData._search to true in the request in jqGrid?.

As I'm struggling with almost the same problem, and just can't get it working - I want to setup "search" and "filters" during the initial loading of the jqGrid - say, on the page reload, and I have my filters stored in the session - and I tried everything I found in Oleg's examples - it just doesn't work!

That's what I'm trying to do -

loadBeforeSend: function (xhr) {
    var grid = jQuery('#' + block_id);
    var postData = grid.jqGrid('getGridParam','postData');
    jQuery.extend(postData,{filters:MyFilters});
    grid.jqGrid('setGridParam', {search: true, postData: postData});
    console.log(grid.jqGrid('getGridParam','postData'));
}

The console printout shows that the filters are in place, but the _search is still false, and the actual Post gets sent even with no filters:

_search   false
block_id  report_block_1table
nd        1297451574526
page      1
rows      25
sidx      id
sord      desc

However, if I put exactly the same code - with the addition of

grid.trigger("reloadGrid");

line - into some button's onClickButton function, and later click the button - everything works; but I need to make it work on "page reload"!

Any ideas? It's driving me crazy...