Have you tried a hard power down yet?
Hold the power button in for ~15 seconds. Ignore the "do you want to shut down" dialog - you do, and holding the power button in will force the issue.
Once the display goes black, hold the power button in for ~10 seconds until you see the screen 'pulse' as the LCD comes on.
Hopefully, once the NC boots back up, it'll be able to stay on.
There have been a couple of other reports in the last week of units doing this, though. If this doesn't fix the problem, I'd call CS about getting a replacement.