Steve,
Just did it again a few times. It's not the Power Kernel 37 crashing, also inconsistent. This time it flashes to some boot screen and then back to boot menu though didn't reboot. Nothing I can do will get it to boot.
It's after booting NITDroid that Maemo 5 crashes and boots the second go. I also found this time that when i had the keyboard closed and tried to reboot, expecting to boot straight to Maemo 5, it still opened the boot menu.
I don't know why or how to get the Power Kernel to boot, at all?