I can not figure out for the life of me why this is erroring - can someone please cast a second pair of eyes over this - it's probably something really stupid, thanks in advance for the help:

EDIT Stupidly I was putting the wrong URL in - HOWEVER... Now I have put the correct URL in, the site just hangs and crashes. Any ideas please?

HTML:

<input id="pc" class="sfc" name="ProdCat[]" type="checkbox" value="">
<input id="psc" class="sfc" name="ProdSubCat[]" type="checkbox" value="">
<input id="bf" class="sfc" name="BrandFil[]" type="checkbox" value="">

JQuery:

$('input[type="checkbox"]').change(function(){

    var name = $(this).attr("name");
    var ProdCatFil = [];
    var ProdSubCatFil = [];
    var BrandFil = [];

    // Loop through the checked checkboxes in the same group
    // and add their values to an array
    $('input[type="checkbox"]:checked').each(function(){

        switch(name) {

           case 'ProdCatFil[]': 
                ProdCatFil.push($(this).val());
                break;

           case 'ProdSubCatFil[]': 
                ProdSubCatFil.push($(this).val());
                break;

           case 'BrandFil[]': 
                BrandFil.push($(this).val());
                break;

        }

    });


    $("#loading").ajaxStart(function(){
        $(this).show();
        $('.content_area').hide();
    });

    $("#loading").ajaxStop(function(){
        $(this).hide();
        $('.content_area').show();
    });

    $.ajax({
        type: "GET",
        url: '../ajax/ajax.php',
        data: 'ProdCatFil='+ProdCatFil+'&ProdSubCatFil='+ProdSubCatFil+'&BrandFil='+BrandFil,
        success: function(data) {
            $('.content_area').html(data);
        }       
    }).error(function (event, jqXHR, ajaxSettings, thrownError) {
        $('.content_area').html("<h2>Could not retrieve data</h2>");
        //alert('[event:' + event + '], [jqXHR:' + jqXHR + '], [ajaxSettings:' + ajaxSettings + '], [thrownError:' + thrownError + '])');
    });

PHP (just to prove it's working):

echo '<h1>TEST TEST TEST </h1>';

The errors from JQuery alert box:

[event:[object Object]], [jqXHR:error], [ajaxSettings:Not Found], [thrownError:undefined])