I have created a USB drive to install a fresh copy of Lion/Mountain Lion. I have had a problem with Lion and Mountain for a while and it is driving me nuts! I know how to create a USB bootable drive, I follow the instructions here to the letter. http://www.macrumors.com/2012/07/25/create-a-bootable-mountain-lion-usb-key-installer/ When i try to boot from the USB drive, all that happes is after about 1 minute it hangs with the attached screen. This happes on more that one mac and more than one USB stick, please HELP! i dont understand what I am doing wrong. Many thanks.