In post #10 he said 'updater can not recognize my device', but he hasn't said how he tried.

@novier
Try to enter preboot by having updater.exe open on your Desktop with a dot beside 'USB Device' with the rgn US fw loaded. Have a usb lead plugged into a rear port of the PC, hold the top left hand corner of the screen and then plug the mini-usb into the nuvi to see if its recognised that way. If it is flash it.