I am trying to boot an Ubuntu 12.10 Live USB on a Dell Inspiron 17r. However, after I boot from the usb, it briefly displays the red screen with keyboard and accessibility icon. It then goes to a black screen with an unmoving line in the top left hand corner. The computer is not making any sounds of activity, and the light on the usb is pulsing slowly, not blinking rapidly as it usually does when running Ubuntu. How can I get my live USB to work the my computer?