Just for clarity...
The "fix" that dave5777 advised has been mentioned here on the Forum a good few times in different threads since the newer 5370 CompactLogix controllers were released.
Selecting the uppermost controller node is not a "fix" to an error as such, but more the correct method to access these newer controllers via their embedded ports.
Users, who are flashing these controllers for the first time, and have previous experience of flashing the older 1769 CompactLogix controllers, are seemingly unaware of the fact that you now simply have to select the controller at its first instance under the communications driver, whether using USB or Ethernet, instead of drilling down to the CompactBus to select it, as you do with the older controllers.
This is because the newer CompactLogix have a simplified path to the embedded ports which exposes the processor more directly as the first hop to external communications.
With the older CompactLogix controllers you have to first access the CompactBus before the processor can be exposed, creating an extra hop for external communications.
This is also why the communications paths you set for message instructions in the newer controllers involve less hops. It is all designed to simplify the communications configuration to and from the controller.
Here is the official guide to using ControlFlash with the old and new CompactLogix controllers. Among other things, it specifically mentions the errors ye are receiving...
44379 - CompactLogix: unable to flash firmware, device is not in the proper mode
Access Level: TechConnect
Regards,
George