I've downloaded the Ubuntu 12.10 iso and followed the instructions on http://www.ubuntu.com/download/help/create-a-usb-stick-on-windows. After I tried the usb disk I got to the Ubuntu live menu, but after choosing run live ubuntu the systems freezes and restarts itself. I've tried this on a Lenovo T61p, an HP pavilion and an Acer Aspire One; all the same results.
you should try unetbootin to make bootable usb it works nice and simple
Or from a terminal:
also available for windows
This sounds like a bad image or bad USB stick or a combination of both:
You can check the integrity of the file you downloaded here:
And after you've made the USB stick use this page to test the installer before you proceed: