None of the buttons respond, not even to power it down. I have a 'spare' brain which has a damaged/cracked LCD screen (my 'first' brain, only a few months old - I learned the hard way to be real careful when dismounting it from the backpack...
). I swapped the button/joystick module since it was really easy to so but this didn't change anything. I also swapped backpacks with my remaining good 'brain - nothing wrong with my 2 backpacks.
Randomly hitting buttons in rapid succession I did once get a message stating 'connect to PC to download software' (I wrote down the full text but it's at home). I connected it to the PC with NSM running but it did not mount to the PC.
I wish I could find another replacement 'brain' to buy to keep my equipment running, I still really like the Neuros II/HD/128 as it has been good to me for 8 years now... no luck thus far 'Googling' for one.