I'm in the same boat. Using Chrome I downloaded all the files last week, thinking I'd do the X2 install this weekend. When I tried the Part1 install and got a 'package integrity check failed' message I stumbled onto this forum thread. I'm now using FDM (performing checksum checks after each download) and am on download attempt #6 on Part1 since every checksum check hasn't matched to this point. What a waste of a weekend...
Followup 10/7/12: Turns out I needed to be on the one machine in the house that's hard-wired to the internet.
Downloading over my wifi resulted in lost packets. Install was easy after that.