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/timthumb0JafxA

Query String : h=120&src=http%3A%2F%2Fwww.tremoschettieri.com%2Fgestione%2Fuploads%2Fphoto%2F71592_3M-ADV-620x460villettaprato.jpg&w=162
TimThumb version : 2.8.13