I'm working with the studyblast solution (http://studyblast.wordpress.com/2011/08/14/guide-mac-os-x-lion-how-to-boot-a-linux-live-system-from-a-usb-drive-how-to-update-any-ocz-ssds-firmware/) to creating a live usb for osx. I managed to get Ubuntu booted but the screen looks like a corrupt/glitch image. I can just about make out the clock on the bottom right and a few icons. I've been told that this is an easy fix and that nomodeset needs to be set for the graphics card but all the solutions i find are for a hard drive installed Ubuntu where you can cd in and edit the grub file - how do you do this is it's in an iso?

Thanks Garrett