I have a self-built Hackintosh, and I've been trying to create and use a live USB drive with Kali Linux on it. So far, I have tried both uNetBootin and the dd method outlined in the documentation, but both have had the exact same result: I choose the USB drive (a Lexar 16 GB) from the boot menu, and it shows a blinking _ or / character in the top left corner of the screen for about five seconds before showing the usual Hackintosh boot screen and booting as if I had chosen my normal boot drive. Any idea what could be causing this problem and how to fix it?

My specs:

Intel Core i5 3570K
8 GB 1333 MHz DDR3 Corsair RAM
NVIDIA GeForce GTX 660
120 GB SanDisk SSD (for booting)
2 512 GB HDD's in a RAID (for storage/backup)

OS X 10.8.4 (12E55)
Kernel Version: Darwin 12.4.0
Using MultiBeast 5.4.1

As a sidenote, I have successfully installed Linux Mint on an identical flash drive and booted it from the same computer with no problems.