Headphones cause system shut down?

[Breathless]

I have a OS X, and every time I pull my headphones in or out of my system, my computer tells me to shut down. I've tried repairing the system and everything with no luck. Any clues as to why this happens??

 

[powermac]

It could be a physical problem, like the connection in the computer could be lose, or faulty. What model Mac do you have ?