Freezing issue and CPU fan error.

I left my machine running for about 24 hours without using it recently. I just came home to find that my machine was frozen and I had to hard reset from the power button, when I rebooted, I got a "CPU Fan error, press F1 to continue" screen.

I've had this once or twice in about a month since I built the machine. However, the fan is running since I'm constantly monitoring the temps. I do not know if the fan stops running when I leave it alone because I'm not able to check. It was running when I came home, I could hear it.

It is an aftermarket Cooler Master V8 instead of the stock heatsink that came with my CPU.