If I understand it correctly, you used xbhdm to lock your HD with a wrong key and your right key (eeprom) is on the HD. In that case, it might be fixable. Unlock your HD with xbhdm. If you locked it with xbhdm, a master password get set. I am not sure what it is tho, but I'll have a look. Then use xbhdm to grab the eeprom from your HD, and lock your HD with this eeprom.
you have to use the atapwd command withing xbhdm
Master Password: XBOXSCENE