After hours of banging my head against the wall trying to create bootable USB sticks on my laptop, I stumbled across this useful titbit of information:
Please notice: While all of the info and above commands are executed properly on a MacBook Air 3,2 (that is the 2010 version 13″ version of the Air) the end result will not produce a bootable USB device, at least not with the image for Ubuntu 10.10 64-bit. When booting of the USB device the following message or something similar will appear: “Missing operating system” and the process is auto-magically halted.
May be useful to somebody. They have a series of steps on the How to install Ubuntu on MacBook using USB Stick page to workaround this but it’s much easier to just find and use another Mac.