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