Have same problem, was updating from OFW 3.56 -> OFW 3.73 with broken BD. It fails at ~67% always and needs to reboot. After turning on it tries to update again and again..
While trying to access recovery mode so: hold power, beep that turns on, beep, turns off, again holding (afterwards wont run), beep that turns on, beeps twice and... keeps updating! No ask for connecting gamepad.
What could I do to restore my PS3 System back to functionality even on old OFW.