Did you check if the fan is running? Most fans have a 3 wire connection. 2 wires are used to power the fan, which rotation speed is controlled by the current, or by using puls-width-modulation. The third wire gives a tacho back (one pulse per rotation, or something like that), which is used by the controller to measure the fan speed.
The most obvious reason for the firmware warning for a non-functioning fan is that it's indeed not functioning, or that the tacho wire has a bad connection.
I did check the fan and I see some dusts on it. I could assume that it was indeed spinning. I have also read somewhere else that the fan will start spinning when temp reaches 60, is this true?