[Plugin: WordPress Content Slide] javascript object not found error

Object does not support this property or method: prototype.js?ver=1.6.1 line 4821 character 5

instanceMethods.getElementsByClassName = Prototype.BrowserFeatures.XPath ?
function(element, className) {
className = className.toString().strip();
var cond = /\s/.test(className) ? $w(className).map(iter).join(”) : iter(className);
return cond ? document._getElementsByXPath(‘.//*’ + cond, element) : [];
} : function(element, className) {
className = className.toString().strip();
var elements = [], classNames = (/\s/.test(className) ? $w(className) : null);
if (!classNames && !className) return elements;
/* Error generated on the following statement from the $(element) */
/* The element has the method but the return from $(element) is null */
var nodes = $(element).getElementsByTagName(‘*’);
className = ‘ ‘ + className + ‘ ‘;

for (var i = 0, child, cn; child = nodes[i]; i++) {
if (child.className && (cn = ‘ ‘ + child.className + ‘ ‘) && (cn.include(className) ||
(classNames && classNames.all(function(name) {
return !name.toString().blank() && cn.include(‘ ‘ + name + ‘ ‘);
}))))
elements.push(Element.extend(child));
}
return elements;
};