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/timthumbv0HvCg

Query String : src=http%3A%2F%2Fwww.elex.it%2Fgestione%2Fuploads%2Fimg%2F14328_1.jpg&w=595&zc=1
TimThumb version : 2.8.13