What is a Nokia FAID?
I brought it into context with firmware updating Nokia phones and came up with this:

The reference states that when the firmware has been altered this happens:


  Your phone should power on at this point but it will keep on restarting and will not receive a signal. 


And further explains why and how to solve it:


  [...] when you alter the flash memory within your phone there are certain security checksums that need to be updated. The checksum that we need to update is called the FAID (Flash Authority ID) [...] it is quite a simple process!