hello!

i'm having some trouble booting kali on my macbook (13" white mid-2010 model) from usb. i used Mac Linux USB Loader to create the bootable drive on a sandisk 8gb flash drive, but when i restart and select one of either drives on rEFIt (bootX64.efi or boot.efi), i select option 1: "boot linux from ISO" or whatever it says, then it loads up a bit and then i get this crazy looking jittery screen : http://i41.tinypic.com/zwhixd.jpg

any help would be much appreciated!