Autoreinstallation image is not signed.

[C. Scott Ananian]

http://wiki.laptop.org/go/Olpc-update#USB_upgrade

You can also boot from the ext2 build on an SD card as a recovery mechanism.

Finally, 8.2 will have better backup/restore functionality, so the
"real" solution then will be reflash+restore.

Please don't use the autoreinstallation key.  It has past its "use by" date.
 --scott
-- 
 ( http://cscott.net/ )