The ISO boots okay here, but the NAND image doesn't seem to.
Empirically, I've found that in order for any rawhide boot to work
on my XO, I must press 'check'. [Otherwise, the firmware (Q2E33)
"gets hung" while sensing the USB devices plugged into the XO.]
With 'check' pressed, my XO doesn't boot 20090312 from NAND. It
completes the (lit background) screen where the output messages from
the firmware are shown (e.g., "Loading ramdisk image ...") -- but
hangs after switching to the dark-background screen -- none of the
(white text on dark) messages from the system loading process itself
get to be shown.
mikus