Hi fadhli,

Please set property UploaderDebug=1, it will open the debug mode.

        <CuteWebUI:Uploader ID="uploader1" runat="server" UploaderDebug="1">
        </CuteWebUI:Uploader>

You can set the temp directory for the uploader control and try again. Ensure that your site has the wire/read permission of the folder you set for. 

Create a folder name "mytemp" under your site root, set it for property "TempDirectory".
 
     <CuteWebUI:Uploader ID="uploader1" runat="server" TempDirectory="~/mytemp">
        </CuteWebUI:Uploader>

Regards,

Ken