MacBook Pro Random Shutdown

"My MBP 3,1 is on logic board #3. When the first two began to fail I would get lots of random kernel panics. Not 'shutdowns' or 'shutoffs' but the lovely multi-lingual kernel panic screen.

If your laptop is just switching off: The only time this has happened to me is when the CPU/GPU are wayyy too hot as mentioned by Chris Johnsen.

Have you checked your logs in Console.app?"