Ok.  Bit daft trying to hack the box with no backups

Have you changed the computers IP address to match the IP required by TFTP?

I think the default ip for the nas becomes 192.168.11.1, so set your computer to 192.168.11.2.

Run TFTP and connect the NAS directly to the computer.  It should see the NAS and take the boot files from the computer.  Then you can force a flash from the PC.
Just do a plain firmware update, as otherwise youll lose the data.

Good Luck!

Run TFTP before turning the box on.

Yeah.  Thats the way Ive done it.  TFTP will keep the line open and intercept the NAS when it polls.

And make sure all firewalls are off.  It can be temperamental.

Doesnt sound drastic tbh, It should be looking for the TFTP during that part.

Are you connected directly to the unit, not going through any switches etc?
If you have any other network adapters, disable them.
Turn off your firewall.
Make sure TFTP is running elevated too.


Edit.
http://buffalo.nas-central.org/wiki/Revive_your_arm9_box_from_scratch

According to that, the PC needs to be on 192.168.11.1

My bad, you need to make sure the PC is 11.1

Elevated means you right click and "Run as Administrator"

Is it XP, Vista or 7?