I remembered OpenELec caused trouble...
As I try to install it from an USB, the TV screen becomes black after 63% (Energy Saving? disabled in TV option).
After the download is (supposed to be ) completed, Swiss Army knife reappears but boots and reload the dl process...
The USB key is not readable on my Mac so I cannot erase the boot folder.
Trying to install on the ATV HD, it says from the Terminal :
"curl -O
http://chewitt.openelec.tv/usb/install-hdd.img.gz
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0Warning: Failed to create the file install-hdd.img.gz: Permission denied
0 11.5M 0 1165 0 0 1661 0 2:01:40 --:--:-- 2:01:40 1659
curl: (23) Failed writing body (0 != 1165)"
Really disappointed compare to how easy it has been to install XBMC 4 years ago...