I tried boot from the internal one after doing chmod 777 and chown -R root on it, and it stuck at "Booting from mmc2 (mmcblk0p1 ext2)..." for around 20 seconds and then it just shut up and started booting up again.
While doing chown, it output "chown: /mmc2/bin/nc: No such file or directory" for a bunch of stuff, even though they are there.
The N800 no longer boots up from flash, so I'll have to restore it. (nothing of value was lost)