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/timthumbNxaioD

Query String : w=640&zc=1&src=http://www.campingmolinoafuoco.com/img/alloggi/lodge_tent/planimetria_lodge_tent.jpg
TimThumb version : 2.8.13