Solution from Eric in LiveSupport: to change Upload Flash type to Iframe Type

 

Please open CuteSoft_Client\CuteEditor\Dialogs\InsertImage.aspx and modify the following code:
<CE:Uploader id="InputFile" runat="server"></CE:Uploader>
 to:
 <CE:Uploader id="InputFile" runat="server" UploadType="Iframe"></CE:Uploader>

And it's now working