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/timthumb8Yjuhs

Query String : h=480&w=640&zc=1&src=http://www.saliceclubresort.com/gestione/uploads/photo/5881_IMG_5401.jpg
TimThumb version : 2.8.13