Hurrah! Updater was able to upload 3760 firmware and now the unit is again up & running. I am thankful to all of you for your advice and support!
The trick to update the firmware was to follow this sequence to enable pre-boot:
FW_RGN --> updater --> Plug in USB--> automatic power on --> press finger
I was used to get into pre-boot mode first and then plug the USB cable
power on --> press finger --> Plug in USB --> FW_RGN --> updater
Such procedure worked fine before the last firmware update.
Regards,
Rodrigo