I created it twice successfully last night, I thought maybe the servers are overloaded so I waited to download the second one until this morning. Checked my Gmail, got the your archive download is ready email, clicked the link, logged into Google's site, clicked Download Archive...mine is several hundred megs in size, it gets between 60 and 150 megs downloaded then again this morning, it quits with the error I described.
Maybe there's some bug relating to the size of my download but I'd think a few hundred megs shouldn't be an issue to download.
Perhaps you should choose a single category (like Gmail) of your Google content, download that, then go back and download another single category until you have it all.
Then I downloaded it and it went fine. So the problem is on Google's side.
The fact that I tried downloading the first archive so many times their service told me finally that I'd downloaded it too many times then the second archive failed around the same rough time frame. Their service is counting the failed downloads as successful, that's bad in itself.