I found a work around that worked for me and I had not seen in these forums. After updating GW2 this afternoon I got the “Download failed! Please check your internet connection and try again. (2)” error. My investigations show no issues with PC or networking. Confirmed this with the GW2.exe -diag command and checked the log “http://wiki.guildwars2.com/wiki/Command_line_arguments”
So I tried a USA VPN service that I use (I’m in Australia) and the update finished. I logged in to the game then logged out, shutdown the VPN and tried logging in again with success on my normal internet connection.