A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = 'text/html' File = /var/www/html/timthumb/cache/timthumbV5UxVQ

Query String : w=520&q=80&s=1&a=c&z=2&src=http://www.ciaocampeggio.it/img/storia/07.jpg
TimThumb version : 2.8.13