Maybe problem with the JQuery syntax, try this:
$(window).load(function(){
var $container = $('#AJpost');
$container.imagesLoaded( function() {
$container.masonry({
itemSelector: '.AJcontainer'
});
});
});
Have a try without imagesLoaded:
$(window).load(function() {
var $container = $('#AJpost');
$container.masonry({
itemSelector: '.AJcontainer'
});
});