[Tiny Clanger]

For future reference, if you can't get it over the network, you should be able to get a login prompt by plugging a USB keyboard into the NUC and pressing Ctrl-Alt-F1 when it's running XBMC (if that doesn't work, try other function keys with Ctrl and Alt held down).

You will need to know nano or vi at this point, though (or you could just rename autostart.sh to something else then fix it over the network, I guess :)