Strange Image Upload and Display Problem

If I upload an image when creating a new product, it is uploaded to the /thumbs folder (permissions 777) but it does not display on the product listing page. I have set the image properties in General Setup>Image to Image Resizing-Landscape and Image Mode-Normal. When running “Inspect” from Google Chrome I see the image has been renamed with a “unknown-” appended to the beginning of it’s name.
This is a new install and has no plugins installed.
Version: 7.1.4
Address: https://micelis-store.com/wp

Thanks,
Frank