Than you fixed it using following code;
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<script type="text/javascript">
Sys.Application.add_init(function () {
$("#<%=FileUpload1.ClientID %>").fileUpload({
'uploader': 'scripts/uploader.swf',
'cancelImg': 'images/cancel.png',
'buttonText': 'Browse Files',
'script': 'Upload.ashx',
'folder': 'uploads',
'fileDesc': 'Image Files',
'fileExt': '*.jpg;*.jpeg;*.gif;*.png',
'multi': true,
'auto': true
});
});
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
function EndRequestHandler(sender, args) {
$("#<%=FileUpload1.ClientID %>").fileUpload({
'uploader': 'scripts/uploader.swf',
'cancelImg': 'images/cancel.png',
'buttonText': 'Browse Files',
'script': 'Upload.ashx',
'folder': 'uploads',
'fileDesc': 'Image Files',
'fileExt': '*.jpg;*.jpeg;*.gif;*.png',
'multi': true,
'auto': true
});
}
</script>