I downloaded Kali from here: http://cdimage.kali.org/kali-images/....0.5-amd64.iso

and when I did a live boot from my USB (after using UNETBOOTIN) I was surprised to find that while the SHA1 hash is the same, I had backtrack files now present on my USB. I don't know if UNETBOOTIN identified the file as a Backtrack distro or if the ISO itself has some problems. I'm completely reformatting the USB then will try again, strange though.....