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/timthumb1p4YNv

Query String : h=744&w=1120&src=http://images.portalimages.com/24206/27903804/image/s2/636629256880139246/b6278e6627ccdb1963694447da8c982358f70488.jpg
TimThumb version : 2.8.14