You shouldn't have had to if the power kernel was installed successfully, it should just be loaded when you reboot. And that's definitely not it.

Also, my bt5.img has an md5sum of ea9da7e254ab93986ceb9164847d8d88. I'm using the one directly downloaded from BackTrack's site though, not the one from page one of this thread. Your problem is definitely that the power kernel isn't running though. I'm not sure why.