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/timthumbpUbQXe

Query String : h=744&w=1120&src=http://images.portalimages.com/24206/29036572/image/s2/637019820862195596/9304ddefa3591dcb4c4d95b4054f0de45e472821.jpg
TimThumb version : 2.8.14