hello,
i had bought this system in october 2012. when i installed ubuntu 12.10 on it, the wifi wouldn't connect. after searching for a long time on different forums, i came across a solution to the problem which involved installing some packages developed by the answerer.
it worked alright, but now I am having problems with upgrading software and downloading some new software from the internet. (i had downloaded softwares before too, the problem has come up recently)

in particular, when i tried to install OCaml on my laptop, these errors came up:

Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu3_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu1_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu1_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu3_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu3_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu3_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...build2_all.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu3_amd64.deb Size mismatch
Failed to fetch http://archive.ubuntu.com/ubuntu/poo...ntu3_amd64.deb Size mismatch
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

does anyone know why I am having this problem and how to solve it?

also, till this problem is solved, it would be great if someone could tell me how to download the files required to install OCaml on ubuntu 12.10 on a flash drive (using windows) and then install it on ubuntu?

thanks