A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = ''/home/hjpughco/public_html/_manage/cache/timthumbukRCgn

Query String : h=744&w=1120&src=http://images.portalimages.com/24206/30568267/image/s2/637540947324247979/3229d57524512de672e2ca17b5856c982839c5b5.jpg
TimThumb version : 2.8.14