The files on our servers (we use the massive Amazon network) are absolutely correct.
If you are unable to complete a download it might be a local problem (reboot your system and router) or some server between the Amazon servers and your computer. All of those are beyond our control. Always try a few hours later. Consider a download manager that can resume broken downloads.
The problem with downloads is that if the first download you go is corrupted in any way the next time you download it the same fault will occur because the copy in the browser cache is used as a guide (and that one is incomplete or faulty). There are two ways of solving this. Either use a different browser if you have one installed or clear the cache of your browser before downloading again. In most browsers this option is located under [options].