The media check says the md5sum is wrong. This implies that there is an error in the media. However, the media check itself is not always right with removable media (it works fine for an .iso file on a hard drive, though), so I would not let that worry you excessively.
When I ran into this situation previously (it happened to me once), after a long investigation, I finally isolated the problem to a failing DVD drive. I replaced the drive and the problem disappeared.
There is another way to get the files, though. Connect to the repositories and download the files directly from there. You can find out how to do such things by checking out this article: