Error: Object doesn't support property or method

[radar]

Alright so I have an error with my ajax.js file.  which atm doesn't include any real ajax.  but im getting an error.

 

var headID = document.getElementsByTagName("head")[0];
loadScript('http://www.thesite.com/site/inc/js/tab.js', headID, 'text/javascript', 'script');
loadScript('http://www.the.com/site/inc/js/prototype.js', headID, 'text/javascript', 'script');

function loadScript(srcs, id, type, element) {
	var tabScript = document.createElement(element);
	tabScript.type = 'text/javascript';
	tabScript.src = srcs;
	id.appendChild(tabScript);
	tabScript.onload=alertArgument(srcs+' is loaded');
}
function UpdateEditorFormValue() { // FUNCTION TO ALLOW FCKEDITOR TO RUN WITH AJAX.
	for ( i = 0; i < parent.frames.length; ++i )
	if ( parent.frames[i].FCK )
	parent.frames[i].FCK.UpdateLinkedField();
}

function addLoadEvent(func) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	} else {
		window.onload = function() {
		oldonload();
		func();
		}
	}
}

// attach an event properly

function attachEvent(element, type, event)	{
  		if(element.attachEvent)	{
    		element.attachEvent('on' + type, event);
	} else {
		element.addEventListener(type, event, false);
	}
}

function alertArgument(myString)	{
  		alert(myString);
}

function attachBehaviors()	{
	attachEvent($('clickme'), "click", function()  {
    	new Ajax.Updater($('updateme'), 'ajax.html', {
   			method:'get', onComplete:function()	{
    			alertArgument('You clicked that thing!')
			}
		})
	});
}

// addLoadEvent(attachBehaviors);

 

its telling me the error is on line 36, which is

element.addEventListener(type, event, false);

 

however, when i remove the lines at the very top of this file to dynamically include protoype.js and tab.js it doesn't throw any errors...  any clue as to why?