Ok, many people are getting bricks because they have rebooted 17 times without powering off the device:

https://bugs.maemo.org/show_bug.cgi?id=6350#c39

To repeat: If you reboot your device 17 times without completely powering it off and disconnecting power, YOU WILL BRICK.

To solve: after a few reboots, make sure you completely power off the system.

If you do brick due to this bug, this is how to recover without reflashing:
http://talk.maemo.org/showthread.php?t=37420


Have fun,

-Jeff
http://wiki.maemo.org/User:Jebba