It's not about my Ubuntu 12.10 x64, but also My Mint Cinnamon x64. When I press shutdown, it becaming shutdown. Power indicator of CPU turn off for a second, then the computer turn on. I have to boot from Windows 7 (loader) to turn off my computer.
It might be the same with this case, but I have multi OS installed on my computer with Windows 7 loader. I have try several ways to solve this problem but nothing happens. I still have to boot from Windows 7 if I have to turn off my computer.