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/timthumbiMjFxL

Query String : q=50&w=1900&h=600&zc=1&s=1&a=c&src=http://www.residenceilgabbiano.it/gestione/uploads/photo/11003_664.jpg
TimThumb version : 2.8.13