Boot up screen says CPU Fan not running Restart computer?

Hello,

If my computer is down for any lenght of time, when I restart it, on the boot up screen it will say CPU Fan not running Restart computer y/n ? I will get down and look and the fan is running. I have changed out the fan 3 times now and after about a month, it will start saying this.
I have an AMD Athlon 1600. Each time, I have taken the fan in to purchase the same one. I don't have any problems with the computer. It does not shut down by it self.
Has anyone else have the problem and can help me fix it.
Thanks.

Sounds like the sensor on the motherboard might be having problems. Don't know how you would fix that (short of trying a new mobo). If you can see the fan is running, I'd say just hit "No" and ignore it.