Linked is the latest firmware that terry personally sent me few months back. It seems like he has dropped support for upgrading firmware. Dont know why. Load the program first, get the usb-serial adapter, , Acc ignition mode on (press the start button without your foot on the pedal), connect the program to the correct com port to connect to the car, upgrade firmware. Easy process.
http://speedy.sh/kvwx3/n55-interface-052011.zip
(Click on the blue title of the file)