ROS-hydro-opencv2 fails to install

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I'm trying to install ROS (ros-hydro-desktop-full), and every time it gets stuck at the same specific place:

Err http: //packages.ros.org/ros/ubuntu/ precise/main ros-hydro-opencv2 amd64
2.4.6-3precise-20140130-1852-+0000   Connection failed [IP: 64.50.236.52 80]

I try pinging the reported IP and it works fine. I have followed the exact same steps as mentioned in the Installation Guide- and the most of the other packages get downloaded fine. This one, and a few more don't:

Err http: //archive.ubuntu.com/ubuntu/ precise/main libboost1.46-dev amd64
1.46.1-7ubuntu3   Connection failed [IP: 91.189.92.200 80]

Err http: //archive.ubuntu.com/ubuntu/ precise/main texlive-binaries amd64 2009-11ubuntu2
  Connection failed [IP: 91.189.91.14 80]

Err http: //archive.ubuntu.com/ubuntu/ precise-updates/main libicu-dev amd64 4.8.1.1-3ubuntu0.1
  Connection failed [IP: 91.189.91.13 80]

Err http: //archive.ubuntu.com/ubuntu/ precise-security/main libicu-dev amd64
4.8.1.1-3ubuntu0.1   Connection failed [IP: 91.189.91.15 80]

It exits with "Unable to correct missing packages." Same story if I try installing these separately.

Could someone please help?

I'm using Ubuntu 12.04.4 (LTS), 64-bit, installed on a Windows partition using Wubi. I have updated and upgraded (many times, actually).