Hi MihaiB,
Yes, for load balancing environment, you need to set the TempDirectory to a a central location, then it will work.
Setting temporary file location in web.config
Add an entry into the <appSettings> section of your application web.config file:
<add key="CuteWebUI.AjaxUploader.TempDirectory" value="~/UploaderTemp"/>
In web farm environments, the Url that you specify must map to a central location, which is saved to by all servers in the farm. This can be done using a virtual directory that maps to a common shared folder on the network.
<add key="CuteWebUI.AjaxUploader.TempDirectory" value="\\shareserver\temp"/>
Regards,
Ken