Looking at the problems above, I would suggest a low level format of the sd card that you will be installing on after reflashing.

Reflash the N8x0
Insert the SD card.
Connect the Nokia to your desktop using the usb cable, make sure that the sd card is not mounted on the Nokia or unmount it using
umount /media/mmcxxxxxx
and then on your desktop

dd if=/dev/zero of=/dev/"whatever your sd card is" (see dmesg output)

Then you can use fdisk to create partitions ,
then make filesystems using
mkfs.vfat /dev/"your sd card partition 1"
mkfs.ext2 /dev/"your sd card partition 2"

unmount from desktop, remove usb cable
and try to do the boot from sd steps again.