Asus P5B Deluxe and CPU Fan Error

[Snowhill]

I have an Asus P5B Deluxe MOBO and Core 2 Duo 6300. Everything is running fine except that on boot up I occasionally get CPU Fan fail error. It's just a message, as I saw with two own eyes that CPU fan is infact running. And the Asus mobo utility (PC probe) also detects that the CPU is working. Is there any way to fix this? Also, my chasis fan sometimes has problem getting detected by PC probe... But all the fans are working properly. Any ideas?