When you mention..."I have done this before with other distributions" do you mean you have been able to boot from a USB stick from the same PC or just that you've done it before?
I'm guessing you're using that USB-creator tool for making these iso files into a bootable setup? I'm sorry I don't have anything but questions, I've not had any luck doing this either.
I did use the Image writer tool and the Ubuntu Netbook remix image to successfully install Ubuntu on my netbook. I just couldn't make Mint work.
On a side note: I had a 1Gb usb drive plugged into my machine at the same time I had my 1
Terrabyte ext. drive plugged in. Hundreds of videos on the 1Tb drive.
Well I hate to say but during the USB creation process I accidentally formatted the wrong drive!