Images are not uploaded. Windows server

Hello.

I have a problem when uploading pics.... they are not shown.

My server is a Windows. I have configured the config.inc.php changing those variables:

$GB_UPLOAD = "../../public/librovisor";
$GB_TMP = "../../public/librovisortmp";

I have tested that a public user can write in those folders... and they can. I have used a test utility given by my provider.
I have had to change into that directory public, because my provider only allow to have public access there inside (and all the folders under it)

When I see the URL of the pic that is not shown I get this:

http://www.vivaelpop.com/public/librovisortmp/img-1113810843.jpg

that is a valid URL... but there inside there is nothing.

Where could be the problem?.

Thanks