Airport Extreme and error -6753 or -6742

Prolem: after firmware upgrade, you cannot connect via airprot utility to the airport.

When doing so you get error -6753 or -6742.

Solution:

Complate firmware reset:

remove power for 30sec, and then reconnect power, press reset botton for +10 seconds.

Then when done, and all is complately reset, set up the airport again to your needs.

Why:

Only apple can anwser, my guess: pure bad design and imcompance from Apple.