Selectable throws an error on click

Selectable throws an error on click


I am getting a:Object doesn't support this property or method when
clicking on <li> in selectable. This happens in IE. Firefox and Chrome
just don't do anything. Error happens on the event = $.Event(event);
line. Anybody else experiencing this problem.
    _trigger: function(type, event, data) {
        var callback = this.options[type],
            eventName = (type == this.widgetEventPrefix
                ? type : this.widgetEventPrefix + type);
        event = $.Event(event);
        event.type = eventName;
Markup looks like this
<ol id="dnn_ctr481_DimensionFilterList_139_selectable">
<li class="ui-widget-content" did="77">
2008/13 (EOY Adj)</li>
<li class="ui-widget-content" did="76">
2008/12 (Aug)</li>
<li class="ui-widget-content" did="75">
2008/11 (Jul)</li>
</ol>
and script that attaches selectable
jQuery("ol[id$=selectable]").selectable();
and I included js files like this
<script src="/tt/DesktopModules/DAF2/js/jquery.nyroModal-1.4.2.js"
type="text/javascript"></script>
<script src="/tt/DesktopModules/DAF/js/ui.core.js" type="text/
javascript"></script>
<script src="/tt/DesktopModules/DAF/js/ui.selectable.js" type="text/
javascript"></script>