The most common cause of this error is having special characters in file names. For security purposes our server does not allow special characters in file names. If you are uploading your photos and one of your files is named something like "New York's #1 Wedding Photographer Logo.jpg" our server will not like the ' or the # in the file name.
Please change your file name to something like logo.jpg and try again. If you continue to have a problem please open a help desk ticket and we'll be happy to investigate.