A couple of questions:
1. Do you mean you have to terminate Updater.exe because it hangs endlessly with 'Software Loading' on the screen?
2. Do you mean it will boot with the US firmware loaded? If it does boot then hard reset it and then clear nonvol memory if that's available to your Oregon:
[Only registered and activated users can see links. Click Here To Register...].
Usually a drastic change in firmware will cause the device to clear nonvol spontaineously on first boot after the flash finishes successfully, 'Locale' has to be re-selected on first boot afterwards. It seems that doesn't happen because the flash isn't completed. You could also try leaving it with updater running for an extended period to see if it will eventually finish the flash itself.