In particular, the error with Stardock Central (I gave it another shot) is "There was a problem downloading the install file for Elemental: Fallen Enchantress: Error retrieving the file due to IOException". This happened at 8% and 30% this time around (I blew away the temporary download file from earlier in case it was the problem).

The servers appear a bit saturated. I'm trying it myself.  It looks like we've brought down Cachefly's server network.  

There is...a way I've found around it.

This is a program I've used to download large files before:

http://internetdownloadmanager.com/

Once you have this installed go to http://download.stardock.com and do this:

Then in the program put the URL here:

I download a lot of large files so I tend to run into this sort of thing.  Stardock Central is generally pretty robust but it's never been put under this kind of strain before. They'll have to improve it tomorrow before we start sending out the emails to existing customers.

I want to emphasize that this is NOT an official recommendation. This is just my personal solution when I download large files off the Internet.

I got it to download via simply retrying on SDCentral multiple times. Each time went a little farther and eventually that all finished. I just wanted to make you aware of the details of the problem with the specific errors, rather than random angry rants I've seen in a couple other threads.

The reason I suspect a cache engine problem is that the HTTP download actually worked fine, it completed and didn't time out, but the file was corrupt and would not install.

The SDCentral download broke multiple times, but the file in the end was complete and valid and installed without error. Something that could be done is simply to make SDCentral retry on error, rather than throw an error to the user and stop.

Based on feedback and error logging on the server, we've put together an updated Stardock Central that should handle some conditions better.

https://stardock.cachefly.net/stardockcentral285-setup.exe

Added checking md5 of chunks after each chunk is written to disk (vs just in memory)
Added retries around the new code path for checking md5 after the chunks were written
Added additional error logging to server (for more verbose reporting of md5 vs file locking timeouts)
Updated file handler to improve compatibility with anti-virus scanning during downloads
Additional retries around in-memory md5 errors
.tmp file directory moved to LOCALAPPDATA\Temp\StardockCentral (to avoid indexing)
Updated error message on some IOException's to suggest temporarily disabling anti-virus

Kris