This problem isn't specially with Ubuntu Live CDs, but I am going crazy trying to figure out how to put an ISO onto a USB stick to boot off.

First, I'll go into GParted and reformat my usb stick to a FAT32.

Then I'll download an ISO or two from FreeNAS (the actual website, not the one that comes with UNetbootin), just as an example, I'll download FreeNAS-8.0.3-RELEASE-p1-x64.iso or FreeNAS-amd64-LiveCD-0.7.2.8191.iso or FreeNAS-amd64-LiveCD-0.7.2.7903.iso. I'll let UNetBootin do it magic work.

Next, I take out the USB stick and put it into another machine and try and boot into the USB stick. But it doesn't work because it gives me the "invalid or corrupt kernel image" error. However, if I let UNetbootin download its own image, it works. But mine doesn't.

I have downloaded these isos over and over, but they haven't worked. However, I burned all of these ISOs to a CD and they work fine.

So...what am I doing wrong and how can I fix it?