[ubuntu] problem with shutdown

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http://ubuntuforums.org – Hi, Sorry for my english first. I just install Ubuntu 12.04 on my new laptop Acer Aspire v5-571 and everything works fine, only one problem.. when i want to shutdown my laptop reboot instead of shutdown. I install laptop mode tools package and now i can shutdown laptop but only when is connected on ac power, when is on battery still reboot instead of shutdown. I need help with this. Thanks. (Hardware)