JavaScript error

Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMViewCSS.getComputedStyle]"  nsresult: "0x80004005 (NS_ERROR_FAILURE)"  location: "JS frame :: http://localhost/whitelynx/cs.fredonia.edu/search.js :: init :: line 113"  data: no]

Code:

// Cross-browser element retrieval function, courtesy of www.quirksmode.org.
function getObj (name)
{
	if (document.getElementById)
	{
		this.obj = document.getElementById (name);
		this.style = document.getElementById (name).style;
	}
	else if (document.all)
	{
		this.obj = document.all[name];
		this.style = document.all[name].style;
	}
	else if (document.layers)
	{
		this.obj = getObjNN4 (document, name);
		this.style = this.obj;
	}
}

function getObjNN4 (obj, name)
{
	var x = obj.layers;
	var foundLayer;
	for (var i=0; i < x.length; i++)
	{
		if (x[i].id == name)
		{
		 	foundLayer = x[i];
		}
		else if (x[i].layers.length)
		{
			var tmp = getObjNN4 (x[i], name);
		}
		if (tmp)
		{
			foundLayer = tmp;
		}
	}
	return foundLayer;
}


function init ()
{
	var searchbox = new getObj ('SearchBox');
	var searchform = new getObj ('SearchForm');
	var searchbutton = new getObj ('SearchButton');

	alert ("ooB!");
	if (searchform.offsetWidth)
	{
		alert ("offsetWidth");
	}
	else if (searchform.currentStyle)
	{
		alert ("currentStyle");
		var newWidth = parseInt (searchform.currentStyle['width']);
		newWidth -= parseInt (searchbutton.currentStyle['width']);
	}
	else if (window.getComputedStyle)
	{
		alert ("getComputedStyle");
		alert (document.defaultView.getComputedStyle (searchform, null).getPropertyValue ('width'));
		alert ("Boo!");
		var newWidth = parseInt (document.defaultView.getComputedStyle (searchform, null).getPropertyValue ('width'));
		newWidth -= parseInt (document.defaultView.getComputedStyle (searchbutton, null).getPropertyValue ('width'));
	}
	else
	{
		alert ("none");
	}
	alert ("ooB!");

	searchbox.style.width = newWidth;

	focusSearchForm ();
}