"There is a problem authenticating your download"

My friend gave me his 7-hour trial key for me to try out SC2, so I started downloading from the blizzard client last night. I woke up and it stopped at 60% and said "There is a problem authenticating your download"...blah blah

Now, since Blizzard and their ****ing stupid forum system won't allow me to post on their SC2 forums, or Blizzard Tech support forums (wtf?), because apparently you need game accounts to do so (Even though I was a loyal WoW customer for 3 years), I am posting this here.

Re-download the installer from another browser to the same location and open it up. Keep all the .part files that you have already. Right click and run as administrator. Worked for me on Windows 7.

Hopefully this will show up in google seach results as people try to get their demos working.