Which version of Ajax Uploader are you using?
Can you try the following code?
<%@ Page language="c#"%>
<%@ Register Namespace="CuteWebUI" Assembly="CuteWebUI.AjaxUploader" TagPrefix="CuteWebUI" %>
<html>
<head>
</head>
<body>
<form id="Form1" method="post" runat="server">
<CuteWebUI:Uploader runat="server" MultipleFilesUpload="true" ID="Uploader1">
</CuteWebUI:Uploader>
</form>
</body>
</html>
asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx