So, I've been working on this for hours and it's getting a little tiring. As some of you may know, installing Ubuntu on Macs is frequently an adventure, and I'm experiencing that right now. The part I'm hung up on at the moment is making a bootable USB. I would just use a CD, but my laptop is a MacBook Air (which doesn't have a CD drive), and I don't own an external CD drive. I initially attempted to use the command line method supplied by the Ubuntu documentation here: https://help.ubuntu.com/community/How%20to%20install%20Ubuntu%20on%20MacBook%20using%20USB%20Stick

However, that wasn't even recognized by rEFIt even when I made a number of different modifications to the process, so I quickly decided to look elsewhere. I came across this guide: https://help.ubuntu.com/community/MacBookAir4-2#Basic_Installation_Instructions

This ended up working to a large extent. If I choose the supplied grub from rEFIt, it will bring me to the Ubuntu grub, asking me to try it, install, or check the disk. And if I choose to boot Linux directly from rEFIt, it will bring me to the language selection menu. But when I make my selection from either of these menus it pauses for about ten seconds and then gives me a command line error message. It begins with kernel panic - not syncing timer doesn't work through interrupt, and then shows about eight file names.

Does anyone here have any ideas as to what can be causing this? I also tried the script with both Ubuntu 11.10 (the current version when the script was written) and 12.04.