You might try booting it with GRUB Legacy.
1: Delete all isolinux and UNetbootin related files and folders
2: Create a file named usbmarkerfile.txt on the root of your drive
3: Download latest GRUB4DOS and extract it and place the files and folders on the root of your drive
4: Download grubinst and run it http://download.gna.org/grubutil/gru...2008-01-01.zip
5: Disk -> Choose your disk -> Refresh - Whole Disk (MBR) - Install
6: Create a file on the root of your drive named menu.lst (NOT .txt!) which contains this:
Code:
title Backtrack 5 R3 X64 Persistent
find --set-root --ignore-floppies --ignore-cd /usbmarkerfile.txt
kernel /casper/ubnkern text splash vga=791-- nouveau.modeset=0 quit noprompt
initrd /casper/ubninit
If you want persistence, create a partition on the drive called EXACTLY casper-rw and make it ext4. Then add "BOOT=casper boot=casper persistent" to the end of the menu.lst entry
Good luck!