Your computer restarted because a problem?

[stanw]

My new iMac froze up and went to a grey screen with a message "Your computer restarted because a problem?" I was simply dragging files into a folder. Any idea why it may have done this?

 

[satcomer]

My new iMac froze up and went to a grey screen with a message "Your computer restarted because a problem?" I was simply dragging files into a folder. Any idea why it may have done this?

That is called a Kernel Panic.