Troubleshooting a sudden shutdown
Solution 1:
Sudden power down could possibly a protection mechanism against overheating. There should be kernel messages regarding this in your error logs at /var/log/kern.log and /var/log/debug
If it's related to overheating:
- What were you doing while the power got cut down? Something CPU / GPU intensive?
- Is your CPU overclocked?
- There are various applications to monitor your temperature, CLI and GUI. One program for the terminal is
sensors(sudo apt-get install lm-sensors). KDE has a Temperature widget, I expect Gnome to have something similar for its panel.