You don't have to use the unit's actual MAC address, as covered in almost all recovery guides - the first few Atheros based buffalo units can use the generic MAC to do TFTP with, for your unit it is:
02:aa:bb:cc:dd:1c
Its with later units that you cannot use the generic MAC for recovery, why buffalo locked it down - i haven't a clue - but imo it was like them shooting theirself in the foot.