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/timthumbKyEF71

Query String : w=640&h=550&zc=2&s=2&src=http://www.residenceilgabbiano.it/img/piantine/casa_ol_bc/2.jpg
TimThumb version : 2.8.13