Powered up a Qu24 yesterday. Screen was black, and the pan pot LEDs were cycling back and forth. Powered it off and on a couple times, no change. Unplugged the AC cable, plugged it back in, and it booted right up.
The power button is indeed a mains switch.
The behaviour you describe is a firmware update, the moving PAN LED’s showing that the console is trying to find a Qu-Drive with firmware on it…
This could happen on boot for a few different reasons, power (or lack of the correct power getting to things to boot them in the correct sequence) being one of them.
If it happens again and you are certain there is nothing wrong with the power (check the blue LED on the rear which will only come on if power is good), then please contact either us or your local distributor to have it checked out.