Download file corrumped
I also had this problems and tried almost everything found on forums, but they didn't work. Then I realized that the ISO i had was of some 1.2GB. But the file originially downloaded as I remembered had been around 2.5GB, and so are the contents of the written disk.
So I found what the problem was. When the downloaded finished downloading the file, it didn't have enough disk space to extract its contents, and it just cropped the end of the iso image. So I checked the files on the written disk and really, many files have contents of zeros (you can check it in the hexa view of totalcmd lister).
The 'funny' part is that the downloader does a CRC check on the downloaded file - but the process failes after the check ...