My computer thinks I'm trying to overclock

I run W7 Professional on a desktop computer with an Asus P9x79 Pro MB, Intel i7 3930k3.2Ghz processor, 16Gb Ram. It's a very stable computer, but suddenly I've had occurrences where the fans ramp up speed and the screens go blank. I power down and when I reboot I get a MB screen and a message to tell me that overclocking failed and to reset my startup options. I go into Bios and restart the machine and it starts happily.
I have no desire to overclock and haven't modified any settings or installed any new software for a while.
What could this be?