CPU Fan error message at boot up

[Slap]

I keep getting this CPU Fan as failed message on startup, if I go into the Bios, I can see that the fan speed is extremely low(300 RPM), but has soon as I start up Windows and check with Asus Prob it is back to normal speeds(1900 RPM)...

Could it be that the fan has dust on the inner mechanism and takes a little while to kick in? Faulty fan? BIOS gone a little weired?

Any suggestions on how best I check the fan?

Cheers


S!ap

PS using a Freezer Pro and have cool and quite turned off in BIOS

 

[Slap]

Thanks for the advice chaps, I will try some of your suggestions.