It's all about your internet connection in that case.
If your internet fail to download a proper installer along with the patch, I'd suggest turning off any program or devices that might be using your bandwidth such as other computer, consoles etc. Shutting down IM programs, downloading software etc.
And then try again.
If you still get broken installers that wont work, you should try downloading the game via torrent.
Download utorrent, then go to the download page and click the "torrent" links. Let the program download the installers for you since they check so the files preventing broken installers.