We have been getting a lot of posts in our forums regarding corrupt installations and downloads. My suggestion is to use Firefox and the Browser Download instead of using the Download Manager.
Downloading Software: Browser Download vs Download Manager - Up and Ready
I have previously posted about using Firefox and DownThemAll to download Autodesk content.
There are some other great third party download managers available - which one do you use?
Jdownloader is quite unique and powerful - check it out if you haven't before. From the website:
It simplifies downloading files from One-Click-Hosters like Rapidshare.com or Megaupload.com - not only for users with a premium account but also for users who don't pay. It offers downloading in multiple parallel streams, captcha recognition, automated file extraction, and much more. Of course, JDownloader is absolutely free of charge.