A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = ''/dati/www/viainternet/cache/timthumbmHzqdG

Query String : h=909&w=1870&zc=3&src=http://www.donalfonso.com/images/gconsulenze_03_g.jpg
TimThumb version : 2.8.11