Yes it is possible that someone else has attempted the 10.6.3 update
Seems trying to get it to boot, or at least get control, is mission impossible, although I have figured out how to slow down (hold any key) the rebooting 'loop' so that I can at least read what the screen says :-
boot 0: done
then rotating dotted line
grey screen
enabling ramdisk....
no preboot ramdisk, not loading postboot ramdisk
efi_inject_get_devprop_string NULL trying stringdata
It then loops again
My USB CD wont stop it with either the OSX retail disk or the NBI disk loaded. I figure maybe a USB flash might do the trick but got to get one tomorrow

---------- Post added at 08:51 PM ---------- Previous post was at 08:25 PM ----------
Oops! As you were. I've managed to get it to read the NBI
Now to see if it will boot from the OSX disk
