Cannot install iOS 5 despite re-installing iTunes, phone hangs at certain point

Hi there,

I cannot seem to install iOS 5 on my iPhone 4. It always hangs at a certain point in the progress bar, about a quarter of the way. I have tried unplugging it and plugging it in again, clicking "Restore and Update", but it still hangs at the same point. And yes, my iTunes is version 10.5, I have re-installed it twice now and the problem still prevails.

Can anyone help me?