"Filename" could not be saved, because the source file could not be read. Try again later, or contact the server administrator.
That's the error you receive, correct?
This usually means that the download was interrupted. This could be the fault of your internet connection or protection software you may be running. (Such as an antivirus or firewall) Since these are larger files, it's entirely possible that your ISP (Internet Service Provider) is capping your download allocation in some way, or is blocking certain activity. Depends on which country you reside in, how the laws are set up, etc.
Make sure you aren't losing your internet connection at any point during the file transfer. If you're using Firefox, make sure to update to the most recent version (older versions had issues downloading files due to the way certain config files were set up), and make sure your download manager (the one built into firefox) is actually turned on. Otherwise, I don't know what other advice to give.