I have installed BT5 on a USB thumb drive, but after I select which mode, I see text flying past the screen, then as the Backtrack splash screen should appear the screen goes black (as in no backlight) and the computer just sits idle. I have tried gnome and KDE. With KDE, I did try text mode, but I only made it to a bare ash shell with a message reading "unable to find a medium containing a live file system". The prompt read "(initramfs)". I'm not a virgin to UNIX/Linux and I've used Backtrack, but I really have no idea what's going on. From that prompt I can see everything on the flash drive so if a script needs to be modified, I might be able to do it (assuming vi is present).
Oh, I've used Lili and unetbootin, same results with either of them.