Comment 4 for bug 1208129

I'm getting the exact same issue!

I know it's not my flash drive I have used it to create a couple of bootables from other ISO's works fine no problems, but I was using UnetBootin before.
I'm having the issue while trying to make a USB bootable from Parted Magic.
For some reason UnetBootin fails everytime to make the usb bootable. It writes the files, but thats all it does do. Never boots no matter how many ways I try it. So I decided to try the startup disk creator. Does exactly the same as your describing. It starts to copy the files across, you think great its working, then blam!

An uncaught exception was raised: unorderable types: NoneType() <= str()

So, I'm still out in the cold as to weather the parted magic iso is dodgy. BUt one things for sure, startup disk creator certainly can't do anything about it,