progressbar error: "F is undefined"

progressbar error: "F is undefined"


I keep on getting this error message from Firebug:
F is undefined
[Break on this error] (function(){var l=this,g,y=l.jQuery,p=l....each
(function(){o.dequeue(this,E)})}});\n
Here are the relevant portions my code:
<head>
<script type="text/javascript">
$(document).ready(function(){$("#progressbar").progressbar({value:
10});});
</script>
</head>
<body>
var progress = null;
update_progressbar();
function update_progressbar(){
progress = $("#progressbar").progressbar('option', 'value');
$("#progressbar").progressbar('option', 'value', progress + 1);
}
</body>
Any thoughts?
Thanks!