Try the reddit link, guys- I just fixed this issue (after struggling with it for 3 hours).
My download speed dropped a couple times, and it took a little longer than usual, but I was able to get the patch installed and was able to run around the Grove 
Here’s another link to the page people are talking about:
http://www.reddit.com/r/Guildwars2/comments/2saub4/how_to_fix_your_updater_temp/
Hope it works!