This has only happened since I updated to Mountain Lion. The firs two times it happened, I came back to a black screen, with occasional audible hard drive activity, and couldn't make anything happen until I just shut it down and rebooted. This afternoon, it froze with a visible screen - except I could move the mouse around on the screen. Very weird, the screen froze at around 2.30 this afternoon, but there's an endless array of kernal entries in the console, starting around 10 minutes before I found the computer locked (which presumably just means that the log got cut off before that point). I have no idea where to go in the logs to see if I can find out what's causing this.

Any suggestions?
If it's brokenless, don't suffix it...