What OS?
What version of BFG?
If you reboot, is it the same one that's not recognized every time?  Or does it change?
What do you have the failing BE plugged into?  Same powered hub as the others?  Have you tried the failing BE with another, to see if it follows the port or the miner?
What have you tried?
Did you post your question to the BFG support thread?

With the lack of info, and not posting this to it's designated support thread... you may get lucky if someone blindly guesses at the problem...

GoodLuck?