jQuery's $.getScript() is buggy sometimes, so I use my own implementation of it like:
jQuery.loadScript = function (url, callback) {
jQuery.ajax({
url: url,
dataType: 'script',
success: callback,
async: true
});
}
and use it like:
if (typeof someObject == 'undefined') $.loadScript('url_to_someScript.js', function(){
//Stuff to do after someScript has loaded
});