I've been working on a multiboot USB using GRUB2's loopback loop feature. However, I can't seem to get Backtrack to successfully boot. It reaches the point where it mounts my local hard drives, but then loops for a while with "NTFS volume version 3.0. kjournald starting. Commit interval 5 seconds. EXT3-fs: mounted filesystem with writeback data mode" before going to a BusyBox prompt. The relevant portion of my grub.cfg file is below. Has anyone had any success?

menuentry "BackTrack 4 Final" {
loopback loop /boot/iso/bt4-final.iso
linux (loop)/boot/vmlinuz find_iso/filename=/boot/iso/bt4-final.iso boot=casper nopersistent vga=normal --
initrd (loop)/boot/initrd.gz
}